JP7345155B2 - Heat retention agent and method for imparting heat retention to articles - Google Patents

Description

The present invention relates to a heat retention agent and a method for imparting heat retention to articles.

Heat retention is considered important in various fields including winter clothing. Clothing, fabrics, etc., where heat retention is important, are usually manufactured using fibers, fabrics, etc. that have high heat retention properties, and various proposals have been made for such high heat retention fibers, fabrics, etc. ing.

For example, Patent Document 1 proposes a knitted fabric that improves heat retention by using a blended yarn of hollow synthetic fibers and synthetic fibers with irregular cross sections, and Patent Document 2 proposes a knitted fabric that increases heat retention by using a blend of hollow synthetic fibers and synthetic fibers with irregular cross sections. A spun yarn containing infrared emitting fine particles is described.

JP2016-56486A Japanese Patent Application Publication No. 2015-124453

Since the highly heat-retaining fabrics and fibers disclosed in Patent Documents 1 and 2 have a special structure, the manufacturing process may be complicated. On the other hand, natural fibers such as wool, cotton, and silk do not have sufficient heat retention properties, and because they are natural, unlike industrial synthetic products, it is difficult to stably obtain products of a certain quality. There was a drawback that it was not easy.

An object of the present invention is to provide a novel heat retention agent. The present invention also aims to provide a method of imparting heat retention to certain articles.

The present inventors have discovered that modified fibroin has excellent heat retention properties. The present invention is based on this new finding.

The present invention relates to the following inventions, for example.
[1]
A heat retention agent containing modified fibroin as an active ingredient.
[2]
The heat retention agent according to [1], wherein the modified fibroin contains modified fibroin having an average value of hydrophobicity index (average HI) of more than 0.
[3]
The heat retention agent according to [1] or [2], wherein the modified fibroin includes modified spider silk fibroin.
[4]
The heat retention agent according to any one of [1] to [3], which is in the form of fibers.
[6]
A method of imparting heat retention to an article, the method comprising:
A method comprising the step of containing modified fibroin in the article.

According to the present invention, it is possible to provide a novel heat retention agent. According to the present invention, it is also possible to provide a method of imparting heat retention to a predetermined article.

According to the present invention, it is possible to impart heat retention without impairing biodegradability by, for example, mixing the heat retention agent according to the present invention into a biodegradable material. can. According to the present invention, the degree of heat retention of a given article can also be adjusted by adjusting the amount of modified fibroin (active ingredient) contained in a given article.

FIG. 2 is a schematic diagram showing an example of a domain sequence of modified fibroin. FIG. 2 is a diagram showing the distribution of z/w (%) values of naturally-derived fibroin. FIG. 2 is a diagram showing the distribution of x/y (%) values of naturally-derived fibroin. FIG. 2 is a schematic diagram showing an example of a domain sequence of modified fibroin. FIG. 2 is a schematic diagram showing an example of a domain sequence of modified fibroin.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated in detail. However, the present invention is not limited to the following embodiments.

[Heat retention agent]
The heat retention agent according to this embodiment contains modified fibroin as an active ingredient.

(modified fibroin)
The modified fibroin according to the present embodiment has a domain sequence represented by formula 1: [(A) _n motif-REP] _m or formula 2: [(A) _n motif-REP] _m - (A) _n motif. It is a protein containing. The modified fibroin may further have an amino acid sequence (N-terminal sequence and C-terminal sequence) added to either or both of the N-terminal side and C-terminal side of the domain sequence. Although the N-terminal sequence and the C-terminal sequence are not limited thereto, typically they are regions that do not have repeated amino acid motifs characteristic of fibroin, and consist of about 100 amino acid residues.

As used herein, "modified fibroin" means artificially produced fibroin (artificial fibroin). The modified fibroin may be a fibroin whose domain sequence is different from the amino acid sequence of naturally occurring fibroin, or may be a fibroin whose domain sequence is the same as the amino acid sequence of naturally occurring fibroin. "Naturally derived fibroin" as used herein is also represented by formula 1: [(A) _n motif-REP] _m or formula 2: [(A) _n motif-REP] _m - (A) _n motif. It is a protein that contains a domain sequence that is

"Modified fibroin" may be one that uses the amino acid sequence of naturally-derived fibroin as is, or one that relies on the amino acid sequence of naturally-derived fibroin and has its amino acid sequence modified (for example, a cloned naturally-derived fibroin). The amino acid sequence may be modified by modifying the gene sequence of fibroin), or it may be artificially designed and synthesized without relying on naturally occurring fibroin (for example, a nucleic acid encoding the designed amino acid sequence). The desired amino acid sequence may be obtained by chemical synthesis).

In this specification, the term "domain sequence" refers to the crystalline region (typically, corresponding to the (A) _n motif of the amino acid sequence) unique to fibroin and the amorphous region (typically, corresponding to the REP of the amino acid sequence). ), and is an amino acid sequence represented by formula 1: [(A) _n motif-REP] _m or formula 2: [(A) _n motif-REP] _m - (A) _n motif. means an array. Here, the (A) _n motif indicates an amino acid sequence consisting mainly of alanine residues, and the number of amino acid residues is 2 to 27. (A) The number of amino acid residues in _{the n} motif may be an integer of 2 to 20, 4 to 27, 4 to 20, 8 to 20, 10 to 20, 4 to 16, 8 to 16, or 10 to 16. . In addition, the ratio of the number of alanine residues to the total number of amino acid residues in the (A) _n motif may be 40% or more, 60% or more, 70% or more, 80% or more, 83% or more, 85% or more, It may be 86% or more, 90% or more, 95% or more, or 100% (meaning that it is composed only of alanine residues). At least seven of the (A) _n motifs present in a plurality in the domain sequence may be composed of only alanine residues. REP indicates an amino acid sequence composed of 2 to 200 amino acid residues. REP may be an amino acid sequence composed of 10-200 amino acid residues. m represents an integer of 2 to 300, and may be an integer of 10 to 300. A plurality of (A) _n motifs may have the same amino acid sequence or may have different amino acid sequences. A plurality of REPs may have the same or different amino acid sequences.

The modified fibroin according to the present embodiment has an amino acid sequence corresponding to, for example, substitution, deletion, insertion, and/or addition of one or more amino acid residues to the cloned naturally occurring fibroin gene sequence. It can be obtained by modifying . Substitutions, deletions, insertions and/or additions of amino acid residues can be performed by methods well known to those skilled in the art, such as site-directed mutagenesis. Specifically, Nucleic Acid Res. 10, 6487 (1982), Methods in Enzymology, 100, 448 (1983), and the like.

Naturally derived fibroin is a protein containing a domain sequence represented by formula 1: [(A) _n motif-REP] _m or formula 2: [(A) _n motif-REP] _m - (A) _n motif. Specific examples include fibroin produced by insects or arachnids.

Examples of fibroin produced by insects include Bombyx mori, Bombyx mandarina, Antheraea yamamai, Anteraea pernyi, and Eriogyna pyret. orum), Pilosamia Cynthia ricini ), Samia cynthia, Caligura japonica, Chussar silkworm (Antheraea mylitta), Muga silkworm (Antheraea assama), and silk proteins produced by silkworms such as simillima xanthoptera) larvae expel Examples include hornet silk protein.

More specific examples of fibroin produced by insects include silkworm fibroin L chain (GenBank accession numbers M76430 (nucleotide sequence) and AAA27840.1 (amino acid sequence)).

Fibroin produced by spiders includes, for example, spiders belonging to the Araneus genus (Araneus genus) such as Araneus spider, Japanese Araneus spider, Red Araneus spider, Blue Araneus spider, and Bean Araneus spider, and Araneus genus Araneus (Araneus genus) such as Araneus Araneus, Araneus Araneus, Araneus Araneus, Brown Araneus spider, and Satsuma flea spider. spiders that belong to the genus Cyrtarachne, such as spiders belonging to the genus Cyrtarachne, such as spiders belonging to the genus Pronus, such as the genus Pronus, spiders that belong to the genus Cyrtarachne, such as the genus Cyrtachne, and genus spiny spiders such as the spiny spider and the staghorn spider. Spiders belonging to the genus Ordgarius (genus Gasteracantha); spiders belonging to the genus Ordgarius (genus Ordgarius), such as the Japanese red-winged spider and spider spider; spiders belonging to the genus Argiope, such as Argiope spiders; Spiders belonging to the genus Arachnura (genus Arachnura); spiders belonging to the genus Acusilas (genus Acusilas), such as the spider spider; ), spiders belonging to the genus Cyclosa (genus Cyclosa), such as the spider spider, spider spider, spider spider, spider spider belonging to the genus Chorizopes, such as the spider spider, and the spider spider, Spiders that belong to the genus Tetragnatha, such as the white-legged spider, the black-legged spider, and the scaly spider; spiders that belong to the genus Leucauge, such as the giant white-backed spider, the white-backed spider, and the white-necked spider; Spiders belonging to the genus Nephila (genus Nephila), spiders belonging to the genus Menosira such as the golden brown spider, spiders belonging to the genus Dyschiriognatha such as the brown recluse spider, black widow spiders, redback spiders, brown widow spiders, brown widow spiders, etc. Examples include spider silk proteins produced by spiders belonging to the Tetragnathidae family, such as spiders belonging to the genus Latrodectus and spiders belonging to the genus Euprosthenops. Examples of spider silk proteins include drag thread proteins such as MaSp (MaSp1 and MaSp2) and ADF (ADF3 and ADF4), MiSp (MiSp1 and MiSp2), and the like.

More specific examples of spider silk proteins produced by arachnids include, for example, fibroin-3 (adf-3) [derived from Araneus diadematus] (GenBank accession numbers AAC47010 (amino acid sequence), U47855 (nucleotide sequence)), fibroin-4 (adf-4) [derived from Araneus diadematus] (GenBank accession numbers AAC47011 (amino acid sequence), U47856 (base sequence)), dragline silk protein spidroin 1 [Nephila clavipe derived from S] (GenBank accession number AAC04504 (amino acid sequence ), U37520 (nucleotide sequence)), major ampullate spidroin 1 [derived from Latrodectus hesperus] (GenBank accession numbers ABR68856 (amino acid sequence), EF595246 (nucleotide sequence)), dragline silk prot ein spidroin 2 [derived from Nephila clavata] (GenBank accession No. AAL32472 (amino acid sequence), AF441245 (base sequence)), major amplate spidroin 1 [derived from Euprosthenops australis] (GenBank accession number CAJ00428 (amino acid sequence), AJ973155 (base sequence)), and major ampullate spidroin 2 [Euprosthenops australis] (GenBank accession number CAM32249.1 (amino acid sequence), AM490169 (nucleotide sequence)), minor amplify silk protein 1 [Nephila clavipes] (GenBank accession number AAC14589.1 (amino acid sequence)), minor a mpullate silk protein 2 [Nephila clavipes] (GenBank accession number AAC14591.1 (amino acid sequence)), minor amplate spidroin-like protein [Nephilengys cruentata] (GenBank accession number ABR37278.1 (amino acid sequence) etc.

A more specific example of naturally-derived fibroin includes fibroin whose sequence information is registered in NCBI GenBank. For example, among sequence information registered in NCBI GenBank that includes INV as DIVISION, spidroin, ampullate, fibroin, "silk and polypeptide", or "silk and protein" are listed as keywords in DEFINITION. This can be confirmed by extracting the sequence, the character string of a specific product from the CDS, and the sequence in which the specific character string is written in TISSUE TYPE from the SOURCE.

The modified fibroin according to the present embodiment may be modified silk fibroin (the amino acid sequence of silk protein produced by silkworms is modified), or modified spider silk fibroin (the amino acid sequence of silk protein produced by spiders is modified). (modified amino acid sequence) may also be used. As the modified fibroin, modified spider silk fibroin is preferred because it has better heat retention properties.

Specific examples of modified fibroin include modified fibroin (first modified fibroin) derived from the large retractor dragline protein produced in the large flial gland of spiders, and a domain sequence with a reduced content of glycine residues. a modified fibroin having a domain sequence with a reduced content of (A) _n motif (a third modified fibroin), a content of glycine residues, and (A) _n Modified fibroin with reduced motif content (fourth modified fibroin), modified fibroin with a domain sequence including a region with a locally large hydrophobicity index (fifth modified fibroin), and content of glutamine residues modified fibroin having a reduced domain sequence (sixth modified fibroin).

The first modified fibroin includes a protein containing a domain sequence represented by formula 1: [(A) _n motif-REP] _m . In the first modified fibroin, the number of amino acid residues in the (A) _n motif is preferably an integer of 3 to 20, more preferably an integer of 4 to 20, even more preferably an integer of 8 to 20, and an integer of 10 to 20. is even more preferred, an integer of 4 to 16 is even more preferred, an integer of 8 to 16 is particularly preferred, and an integer of 10 to 16 is most preferred. In the first modified fibroin, the number of amino acid residues constituting REP in Formula 1 is preferably 10 to 200 residues, more preferably 10 to 150 residues, and 20 to 100 residues. It is more preferable that the number of residues is 20 to 75, and even more preferable that the number of residues is 20 to 75. The first modified fibroin has amino acid residues in which the total number of glycine residues, serine residues, and alanine residues contained in the amino acid sequence represented by formula 1: [(A) _n motif-REP] _m It is preferably 40% or more, more preferably 60% or more, and even more preferably 70% or more of the total number.

The first modified fibroin contains an amino acid sequence unit represented by formula 1: [(A) _n motif-REP] _m , and has an amino acid sequence whose C-terminal sequence is shown in any of SEQ ID NOs: 1 to 3, or It may be a polypeptide having an amino acid sequence having 90% or more homology with the amino acid sequence shown in any of SEQ ID NOs: 1 to 3.

The amino acid sequence shown in SEQ ID NO: 1 is the same as the amino acid sequence consisting of the C-terminal 50 amino acid residues of the amino acid sequence of ADF3 (GI: 1263287, NCBI), and the amino acid sequence shown in SEQ ID NO: 2 is the same as that of ADF3 (GI: 1263287, NCBI). The amino acid sequence shown in SEQ ID NO: 3 is the same as that obtained by removing 20 residues from the C-terminus of the amino acid sequence shown in SEQ ID NO: 1, and the amino acid sequence shown in SEQ ID NO: 1 is obtained by removing 29 residues from the C-terminus of the amino acid sequence shown in SEQ ID NO: 1. Identical to the amino acid sequence.

As a more specific example of the first modified fibroin, (1-i) the amino acid sequence shown by SEQ ID NO: 4 (recombinant spider silk protein ADF3KaiLargeNRSH1), or (1-ii) the amino acid sequence shown by SEQ ID NO: 4 and 90 Mention may be made of modified fibroin comprising amino acid sequences having % or more sequence identity. Preferably, the sequence identity is 95% or more.

The amino acid sequence shown by SEQ ID NO: 4 is the amino acid sequence of ADF3 with an amino acid sequence (SEQ ID NO: 5) consisting of a start codon, a His10 tag, and an HRV3C protease (Human rhinovirus 3C protease) recognition site added to the N-terminus. The 13th repeat region has been increased approximately twice as much, and the translation has been mutated so that it terminates at the 1154th amino acid residue. The C-terminal amino acid sequence of the amino acid sequence shown by SEQ ID NO: 4 is the same as the amino acid sequence shown by SEQ ID NO: 3.

The modified fibroin (1-i) may consist of the amino acid sequence shown in SEQ ID NO: 4.

The second modified fibroin has an amino acid sequence whose domain sequence has a reduced content of glycine residues compared to naturally occurring fibroin. The second modified fibroin can be said to have an amino acid sequence that corresponds to at least one or more glycine residues in REP being substituted with another amino acid residue, compared to naturally occurring fibroin. .

The second modified fibroin has a domain sequence of GGX and GPGXX in REP (where G is a glycine residue, P is a proline residue, and X is an amino acid residue other than glycine), compared to naturally-derived fibroin. ) has an amino acid sequence corresponding to the substitution of one glycine residue in at least one or more of the motif sequences with another amino acid residue. It's okay.

In the second modified fibroin, the proportion of the motif sequence in which the above-mentioned glycine residue is substituted with another amino acid residue may be 10% or more of the total motif sequence.

The second modified fibroin includes a domain sequence represented by formula 1: [(A) _n motif-REP] _m , and from the above domain sequence, from the (A) _n motif located at the most C-terminal side to the above domain sequence. Let z be the total number of amino acid residues in the amino acid sequence consisting of z/w is 30% or more, where w is the total number of amino acid residues in the sequence excluding the sequence from the (A) _n motif located on the most C-terminal side to the C-terminus of the above domain sequence, It may have an amino acid sequence of 40% or more, 50% or more, or 50.9% or more. (A) The number of alanine residues relative to the total number of amino acid residues in the _n motif may be 83% or more, preferably 86% or more, more preferably 90% or more, and 95% or more. It is more preferable that it be present, and even more preferable that it be 100% (meaning that it is composed only of alanine residues).

The second modified fibroin preferably has an increased content of an amino acid sequence consisting of XGX by replacing one glycine residue of the GGX motif with another amino acid residue. The content of the amino acid sequence consisting of GGX in the domain sequence of the second modified fibroin is preferably 30% or less, more preferably 20% or less, even more preferably 10% or less, and 6 % or less, even more preferably 4% or less, and particularly preferably 2% or less. The content ratio of the amino acid sequence consisting of GGX in the domain sequence can be calculated by the same method as the method for calculating the content ratio (z/w) of the amino acid sequence consisting of XGX below.

The method for calculating z/w will be explained in more detail. First, in fibroin (modified fibroin or naturally-derived fibroin) containing a domain sequence represented by formula 1: [(A) _n motif-REP] _m , (A) _n is located closest to the C-terminus from the domain sequence. Amino acid sequences consisting of XGX are extracted from all REPs included in the sequence excluding the sequence from the motif to the C-terminus of the domain sequence. The total number of amino acid residues constituting XGX is z. For example, if 50 amino acid sequences consisting of XGX are extracted (no overlap), z is 50×3=150. In addition, for example, in the case of an amino acid sequence consisting of XGXGX, if there is an X included in two XGX (center be). w is the total number of amino acid residues contained in the domain sequence excluding the sequence from the (A) _n motif located on the C-terminal side to the C-terminus of the domain sequence. For example, in the case of the domain sequence shown in FIG. 1, w is 4+50+4+100+4+10+4+20+4+30=230 (excluding the (A) _n motif located on the most C-terminal side). Next, by dividing z by w, z/w (%) can be calculated.

Here, z/w in naturally derived fibroin will be explained. First, as described above, when fibroin whose amino acid sequence information is registered in NCBI GenBank was confirmed by the method described above, 663 types of fibroin (415 types of fibroin derived from arachnids) were extracted. Of all the extracted fibroin, naturally derived fibroin contains a domain sequence represented by formula 1: [(A) _n motif-REP] _m , and the content of the amino acid sequence consisting of GGX in fibroin is 6% or less. From the amino acid sequence of fibroin, z/w was calculated using the calculation method described above. The results are shown in FIG. The horizontal axis of FIG. 2 shows z/w (%), and the vertical axis shows frequency. As is clear from FIG. 2, the z/w of naturally derived fibroin is less than 50.9% (the highest is 50.86%).

In the second modified fibroin, z/w is preferably 50.9% or more, more preferably 56.1% or more, even more preferably 58.7% or more, and 70% or more. Even more preferably, it is 80% or more. The upper limit of z/w is not particularly limited, but may be, for example, 95% or less.

The second modified fibroin can be produced, for example, by modifying the cloned naturally occurring fibroin gene sequence so that it encodes another amino acid residue by replacing at least a portion of the base sequence encoding a glycine residue. Obtainable. At this time, one glycine residue in the GGX motif and GPGXX motif may be selected as the glycine residue to be modified, or may be substituted so that z/w is 50.9% or more. It can also be obtained, for example, by designing an amino acid sequence that satisfies the above aspects from the amino acid sequence of naturally occurring fibroin, and chemically synthesizing a nucleic acid encoding the designed amino acid sequence. In either case, in addition to the modification equivalent to replacing the glycine residue in REP with another amino acid residue from the amino acid sequence of naturally-derived fibroin, one or more amino acid residues are further substituted or deleted. , insertion and/or addition may be made to the amino acid sequence.

The above-mentioned other amino acid residues are not particularly limited as long as they are amino acid residues other than glycine residues, but include valine (V) residues, leucine (L) residues, isoleucine (I) residues, methionine ( M) residues, hydrophobic amino acid residues such as proline (P) residues, phenylalanine (F) residues and tryptophan (W) residues, glutamine (Q) residues, asparagine (N) residues, serine (S ) residues, lysine (K) residues, and glutamic acid (E) residues are preferred, and valine (V) residues, leucine (L) residues, isoleucine (I) residues, phenylalanine ( F) residues and glutamine (Q) residues are more preferred, and glutamine (Q) residues are even more preferred.

As a more specific example of the second modified fibroin, (2-i) SEQ ID NO: 6 (Met-PRT380), SEQ ID NO: 7 (Met-PRT410), SEQ ID NO: 8 (Met-PRT525), or SEQ ID NO: 9 (Met -PRT799), or (2-ii) an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, Mention may be made of modified fibroin.

The modified fibroin (2-i) will be explained. The amino acid sequence shown by SEQ ID NO: 6 is obtained by replacing all GGX in REP of the amino acid sequence shown by SEQ ID NO: 10 (Met-PRT313), which corresponds to naturally occurring fibroin, with GQX. The amino acid sequence shown by SEQ ID NO: 7 is obtained by deleting every two (A) _n motifs from the amino acid sequence shown by SEQ ID NO: 6 from the N-terminal side to the C-terminal side, and further before the C-terminal sequence. One [(A) _{n-motif-REP] is inserted into the [(A) n-} motif-REP]. The amino acid sequence shown by SEQ ID NO: 8 is obtained by inserting two alanine residues at the C-terminal side of each (A) _n motif of the amino acid sequence shown by SEQ ID NO: 7, and further adding some glutamine (Q) residues. It is substituted with a serine (S) residue and some amino acids on the C-terminal side are deleted so that the molecular weight is almost the same as that of SEQ ID NO: 7. The amino acid sequence shown by SEQ ID NO: 9 is a region of 20 domain sequences present in the amino acid sequence shown by SEQ ID NO: 7 (however, several amino acid residues on the C-terminal side of the region are substituted). A predetermined hinge sequence and His tag sequence are added to the C-terminus of a sequence that is repeated four times.

The value of z/w in the amino acid sequence shown by SEQ ID NO: 10 (corresponding to naturally occurring fibroin) is 46.8%. The value of z/w in the amino acid sequence shown by SEQ ID NO: 6, the amino acid sequence shown by SEQ ID NO: 7, the amino acid sequence shown by SEQ ID NO: 8, and the amino acid sequence shown by SEQ ID NO: 9 is 58.7%, respectively. They are 70.1%, 66.1% and 70.0%. In addition, the values of x/y at the jagged ratio (described later) of 1:1.8 to 11.3 of the amino acid sequences shown by SEQ ID NO: 10, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, and SEQ ID NO: 9 are: They are 15.0%, 15.0%, 93.4%, 92.7% and 89.8%, respectively.

The modified fibroin (2-i) may consist of the amino acid sequence shown in SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, or SEQ ID NO: 9.

The modified fibroin (2-ii) contains an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown by SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9. The modified fibroin (2-ii) is also a protein containing a domain sequence represented by formula 1: [(A) _n motif-REP] _m . The sequence identity is preferably 95% or more.

The modified fibroin (2-ii) has 90% or more sequence identity with the amino acid sequence shown by SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, and has XGX ( However, when z is the total number of amino acid residues in the amino acid sequence consisting of is preferably 50.9% or more.

The second modified fibroin may contain a tag sequence at either or both of the N-terminus and C-terminus. This makes it possible to isolate, immobilize, detect, visualize, etc. the modified fibroin.

Examples of tag sequences include affinity tags that utilize specific affinity (binding ability, affinity) with other molecules. A specific example of the affinity tag is a histidine tag (His tag). The His tag is a short peptide with about 4 to 10 histidine residues arranged in a row, and has the property of specifically binding to metal ions such as nickel, making it possible to isolate modified fibroin by chelating metal chromatography. It can be used for. A specific example of the tag sequence is, for example, the amino acid sequence shown by SEQ ID NO: 11 (an amino acid sequence including a His tag sequence and a hinge sequence).

Furthermore, tag sequences such as glutathione-S-transferase (GST), which specifically binds to glutathione, and maltose binding protein (MBP), which specifically binds to maltose, can also be used.

Furthermore, "epitope tags" that utilize antigen-antibody reactions can also be used. By adding a peptide (epitope) exhibiting antigenicity as a tag sequence, an antibody against the epitope can be bound. Examples of epitope tags include HA (peptide sequence of influenza virus hemagglutinin) tag, myc tag, FLAG tag, and the like. By using epitope tags, modified fibroin can be easily purified with high specificity.

Furthermore, it is also possible to use tag sequences whose tag sequences can be cleaved with a specific protease. Modified fibroin from which the tag sequence has been removed can also be recovered by treating the protein adsorbed via the tag sequence with a protease.

More specific examples of modified fibroin containing a tag sequence include (2-iii) the amino acid represented by SEQ ID NO: 12 (PRT380), SEQ ID NO: 13 (PRT410), SEQ ID NO: 14 (PRT525), or SEQ ID NO: 15 (PRT799); or (2-iv) a modified fibroin comprising an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, or SEQ ID NO: 15. .

The amino acid sequences shown by SEQ ID NO: 16 (PRT313), SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14 and SEQ ID NO: 15 are SEQ ID NO: 10, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8 and SEQ ID NO: 9, respectively. The amino acid sequence shown in SEQ ID NO: 11 (including the His tag sequence and hinge sequence) is added to the N-terminus of the shown amino acid sequence.

The modified fibroin (2-iii) may consist of the amino acid sequence shown by SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, or SEQ ID NO: 15.

The modified fibroin (2-iv) contains an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, or SEQ ID NO: 15. The modified fibroin (2-iv) is also a protein containing a domain sequence represented by formula 1: [(A) _n motif-REP] _m . The sequence identity is preferably 95% or more.

The modified fibroin (2-iv) has 90% or more sequence identity with the amino acid sequence shown by SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, or SEQ ID NO: 15, and has XGX ( However, when z is the total number of amino acid residues in the amino acid sequence consisting of is preferably 50.9% or more.

The second modified fibroin may contain a secretion signal for releasing the protein produced in the recombinant protein production system to the outside of the host. The sequence of the secretion signal can be appropriately set depending on the type of host.

The third modified fibroin has an amino acid sequence in which the content of the (A) _n motif is reduced in the domain sequence compared to naturally occurring fibroin. The domain sequence of the third modified fibroin can be said to have an amino acid sequence corresponding to the deletion of at least one or more (A) _n motifs compared to naturally occurring fibroin.

The third modified fibroin may have an amino acid sequence corresponding to a 10 to 40% deletion of the (A) _n motif from naturally occurring fibroin.

The third modified fibroin has a domain sequence that is at least one (A) _n motif for every one to three (A) _n motifs from the N-terminal side to the C-terminal side, compared to naturally-derived fibroin. may have an amino acid sequence corresponding to the deletion.

The third modified fibroin has a domain sequence that is at least two consecutive (A) _n motifs deleted from the N-terminus to the C-terminus, and one (A ) It may have an amino acid sequence corresponding to deletions of _{the n} motif repeated in this order.

The third modified fibroin may have an amino acid sequence whose domain sequence corresponds to deletion of (A) _n motif from every second domain sequence from the N-terminal side to the C-terminal side. .

The third modified fibroin contains a domain sequence represented by formula 1: [(A) _n motif-REP] _m , and two adjacent [(A) _n motifs from the N-terminal side toward the C-terminal side. -REP] sequentially compare the number of amino acid residues of the REPs in the unit, and when the number of amino acid residues of the REP with the smallest number of amino acid residues is set as 1, the ratio of the number of amino acid residues of the other REP is 1.8 ~ 11.3, where x is the maximum value of the sum of the numbers of amino acid residues in two adjacent [(A) _n motif-REP] units, and y is the total number of amino acid residues in the domain sequence. Furthermore, it may have an amino acid sequence in which x/y is 20% or more, 30% or more, 40% or more, or 50% or more. (A) The number of alanine residues relative to the total number of amino acid residues in the _n motif may be 83% or more, preferably 86% or more, more preferably 90% or more, and 95% or more. It is more preferable that it be present, and even more preferable that it be 100% (meaning that it is composed only of alanine residues).

The method for calculating x/y will be explained in more detail with reference to FIG. FIG. 1 shows the domain sequence of modified fibroin with the N-terminal sequence and C-terminal sequence removed. The domain sequence is from the N-terminal side (left side): (A) _n motif - 1st REP (50 amino acid residues) - (A) _n motif - 2nd REP (100 amino acid residues) - (A) _n Motif - 3rd REP (10 amino acid residues) - (A) _n motif - 4th REP (20 amino acid residues) - (A) _n motif - 5th REP (30 amino acid residues) - (A) It has a sequence called _n motif.

Two adjacent [(A) _n- motif-REP] units are selected sequentially from the N-terminus to the C-terminus so that there is no overlap. At this time, there may be an unselected [(A) _n motif-REP] unit. FIG. 1 shows pattern 1 (comparison of first REP and second REP, and comparison of third REP and fourth REP), pattern 2 (comparison of first REP and second REP, and Pattern 3 (Comparison of the 2nd REP and the 3rd REP, and Comparison of the 4th REP and the 5th REP), Pattern 4 (Comparison of the 1st REP and the 5th REP) A comparison of the second REP) was shown. Note that there are other selection methods besides this.

Next, for each pattern, the number of amino acid residues of each REP in the two selected adjacent [(A) _n motif-REP] units is compared. The comparison is performed by determining the ratio of the number of amino acid residues of the other amino acid residue, when the one with the smaller number of amino acid residues is set to 1. For example, when comparing the first REP (50 amino acid residues) and the second REP (100 amino acid residues), if the first REP with fewer amino acid residues is set as 1, then the second REP The ratio of the number of amino acid residues is 100/50=2. Similarly, when comparing the fourth REP (20 amino acid residues) and the fifth REP (30 amino acid residues), when the fourth REP with fewer amino acid residues is set as 1, the fifth REP The ratio of the number of amino acid residues is 30/20=1.5.

In Figure 1, when the one with the smaller number of amino acid residues is set as 1, the set of [(A) _n motif-REP] units in which the ratio of the number of amino acid residues of the other one is 1.8 to 11.3 is Indicated by a solid line. In this specification, this ratio is referred to as the jagged ratio. When the one with the smaller number of amino acid residues is set as 1, the pair of [(A) _n motif-REP] units in which the ratio of the number of amino acid residues of the other one is less than 1.8 or more than 11.3 is indicated by a broken line. Indicated.

For each pattern, add all the numbers of amino acid residues in the two adjacent [(A) _n motif - REP] units shown by solid lines (not only the number of amino acid residues in REP but also the number of amino acid residues in the (A) _n motif). be.). Then, the added total values are compared, and the total value of the pattern in which the total value is the maximum (the maximum value of the total values) is set as x. In the example shown in FIG. 1, the total value of pattern 1 is the largest.

Next, x/y (%) can be calculated by dividing x by the total number of amino acid residues y in the domain sequence.

In the third modified fibroin, x/y is preferably 50% or more, more preferably 60% or more, even more preferably 65% or more, and even more preferably 70% or more. It is preferably at least 75%, even more preferably at least 80%, particularly preferably at least 80%. The upper limit of x/y is not particularly limited, and may be, for example, 100% or less. When the serration ratio is 1:1.9 to 11.3, x/y is preferably 89.6% or more, and when the serration ratio is 1:1.8 to 3.4, x/y is preferably 89.6% or more. /y is preferably 77.1% or more, and when the jagged ratio is 1:1.9 to 8.4, x/y is preferably 75.9% or more, and the jagged ratio is 1:1.9 to 8.4. : 1.9 to 4.1, x/y is preferably 64.2% or more.

If the third modified fibroin is a modified fibroin in which there is a plurality of modified fibroin in the domain sequence (A) in which at least seven of _{the n} motifs are composed of only alanine residues, x/y must be 46.4% or more. is preferably at least 50%, even more preferably at least 55%, even more preferably at least 60%, even more preferably at least 70%, and even more preferably at least 80%. It is particularly preferable that there be. There is no particular restriction on the upper limit of x/y, as long as it is 100% or less.

Here, x/y in naturally derived fibroin will be explained. First, as described above, when fibroin whose amino acid sequence information is registered in NCBI GenBank was confirmed by the method described above, 663 types of fibroin (415 types of fibroin derived from arachnids) were extracted. Of all the extracted fibroins, from the amino acid sequence of naturally occurring fibroin consisting of the domain sequence represented by formula 1: [(A) _n motif-REP] _m , x/y was calculated. Figure 3 shows the results when the jaggedness ratio is 1:1.9 to 4.1.

The horizontal axis of FIG. 3 indicates x/y (%), and the vertical axis indicates frequency. As is clear from FIG. 3, x/y in naturally derived fibroin is less than 64.2% (the highest is 64.14%).

The third modified fibroin is obtained by, for example, deleting one or more sequences encoding the (A) _n motif from the cloned naturally occurring fibroin gene sequence so that x/y is 64.2% or more. This can be obtained by For example, from the amino acid sequence of naturally-derived fibroin, an amino acid sequence corresponding to the deletion of one or more (A) _n motifs such that x/y is 64.2% or more can be designed. It can also be obtained by chemically synthesizing a nucleic acid encoding the amino acid sequence. In either case, in addition to the modification corresponding to the deletion of (A) _n motif from the amino acid sequence of naturally-derived fibroin, one or more amino acid residues are further substituted, deleted, inserted, and/or added. The amino acid sequence may be modified to correspond to the above.

As a more specific example of the third modified fibroin, (3-i) SEQ ID NO: 17 (Met-PRT399), SEQ ID NO: 7 (Met-PRT410), SEQ ID NO: 8 (Met-PRT525), or SEQ ID NO: 9 (Met -PRT799), or (3-ii) an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 17, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, Mention may be made of modified fibroin.

The modified fibroin (3-i) will be explained. The amino acid sequence shown by SEQ ID NO: 17 is derived from the amino acid sequence shown by SEQ ID NO: 10 (Met-PRT313), which corresponds to naturally occurring fibroin, from the N-terminal side to the C-terminal side every two (A) _n The motif is deleted and one [(A) _n motif-REP] is inserted before the C-terminal sequence. The amino acid sequence shown by SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9 is as explained for the second modified fibroin.

The x/y value of the amino acid sequence shown by SEQ ID NO: 10 (corresponding to naturally occurring fibroin) at a jagged ratio of 1:1.8 to 11.3 is 15.0%. The value of x/y in both the amino acid sequence shown by SEQ ID NO: 17 and the amino acid sequence shown by SEQ ID NO: 7 is 93.4%. The value of x/y in the amino acid sequence shown by SEQ ID NO: 8 is 92.7%. The value of x/y in the amino acid sequence shown by SEQ ID NO: 9 is 89.8%. The values of z/w in the amino acid sequences shown by SEQ ID NO: 10, SEQ ID NO: 17, SEQ ID NO: 7, SEQ ID NO: 8, and SEQ ID NO: 9 are 46.8%, 56.2%, 70.1%, and 66.9%, respectively. 1% and 70.0%.

The modified fibroin (3-i) may consist of the amino acid sequence shown in SEQ ID NO: 17, SEQ ID NO: 7, SEQ ID NO: 8, or SEQ ID NO: 9.

The modified fibroin (3-ii) contains an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 17, SEQ ID NO: 7, SEQ ID NO: 8, or SEQ ID NO: 9. The modified fibroin (3-ii) is also a protein containing a domain sequence represented by formula 1: [(A) _n motif-REP] _m . The sequence identity is preferably 95% or more.

The modified fibroin of (3-ii) has 90% or more sequence identity with the amino acid sequence shown by SEQ ID NO: 17, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, and has a sequence identity of 90% or more from the N-terminal side to the C-terminal side. The number of amino acid residues in the REPs of two adjacent [(A) _n motif-REP] units are compared sequentially, and when the number of amino acid residues in the REP with the smallest number of amino acid residues is set as 1, The amino acid residues of two adjacent [(A) _n motif-REP] units in which the ratio of the number of amino acid residues of REP is 1.8 to 11.3 (ratio of 1:1.8 to 11.3) When the maximum value of the sum of the base numbers is x and the total number of amino acid residues in the domain sequence is y, it is preferable that x/y is 64.2% or more.

The third modified fibroin may contain the above-described tag sequence at either or both of the N-terminus and C-terminus.

More specific examples of modified fibroin containing a tag sequence include (3-iii) the amino acids shown by SEQ ID NO: 18 (PRT399), SEQ ID NO: 13 (PRT410), SEQ ID NO: 14 (PRT525), or SEQ ID NO: 15 (PRT799); or (3-iv) a modified fibroin comprising an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 18, SEQ ID NO: 13, SEQ ID NO: 14, or SEQ ID NO: 15. .

The amino acid sequences shown by SEQ ID NO: 18, SEQ ID NO: 13, SEQ ID NO: 14 and SEQ ID NO: 15 are the amino acid sequences shown by SEQ ID NO: 17, SEQ ID NO: 7, SEQ ID NO: 8 and SEQ ID NO: 9, respectively. The amino acid sequence shown in (including His tag sequence and hinge sequence) is added.

The modified fibroin (3-iii) may consist of the amino acid sequence shown by SEQ ID NO: 18, SEQ ID NO: 13, SEQ ID NO: 14, or SEQ ID NO: 15.

The modified fibroin (3-iv) contains an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 18, SEQ ID NO: 13, SEQ ID NO: 14, or SEQ ID NO: 15. The modified fibroin (3-iv) is also a protein containing a domain sequence represented by formula 1: [(A) _n motif-REP] _m . The sequence identity is preferably 95% or more.

The modified fibroin of (3-iv) has 90% or more sequence identity with the amino acid sequence shown by SEQ ID NO: 18, SEQ ID NO: 13, SEQ ID NO: 14, or SEQ ID NO: 15, and has a sequence identity from the N-terminus to the C-terminus. The number of amino acid residues in the REPs of two adjacent [(A) _n motif-REP] units are compared sequentially, and when the number of amino acid residues in the REP with the smallest number of amino acid residues is set as 1, Let x be the maximum value of the sum of the numbers of amino acid residues of two adjacent [(A) _n motif-REP] units where the ratio of the number of amino acid residues of REP is 1.8 to 11.3. , x/y is preferably 64.2% or more, where y is the total number of amino acid residues in the domain sequence.

The third modified fibroin may contain a secretion signal for releasing the protein produced in the recombinant protein production system to the outside of the host. The sequence of the secretion signal can be appropriately set depending on the type of host.

The fourth modified fibroin has a domain sequence that has a reduced content of (A) _n motifs as well as an amino acid sequence that has a reduced content of glycine residues compared to naturally-derived fibroin. It is something that you have. The fourth modified fibroin has a domain sequence in which at least one or more (A) _n motifs are deleted compared to naturally occurring fibroin, and in addition, at least one or more glycine residues in REP are deleted. It can be said to have an amino acid sequence corresponding to substitution with another amino acid residue. That is, the fourth modified fibroin is a modified fibroin that has both the characteristics of the above-described second modified fibroin and the third modified fibroin. Specific aspects are as described for the second modified fibroin and the third modified fibroin.

More specific examples of the fourth modified fibroin include (4-i) SEQ ID NO: 7 (Met-PRT410), SEQ ID NO: 8 (Met-PRT525), SEQ ID NO: 9 (Met-PRT799), and SEQ ID NO: 13 (PRT410). ), the amino acid sequence shown by SEQ ID NO: 14 (PRT525) or SEQ ID NO: 15 (PRT799), or (4-ii) SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 13, SEQ ID NO: 14 or SEQ ID NO: 15 Examples of modified fibroin include an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in . Specific embodiments of the modified fibroin comprising the amino acid sequence shown by SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 13, SEQ ID NO: 14, or SEQ ID NO: 15 are as described above.

The fifth modified fibroin has a domain sequence in which one or more amino acid residues in REP are substituted with amino acid residues having a large hydrophobicity index compared to naturally occurring fibroin, and/or REP It may have an amino acid sequence that includes a region with a locally large hydrophobic index, which corresponds to the insertion of one or more amino acid residues with a large hydrophobic index.

Preferably, a region with a locally large hydrophobicity index is composed of 2 to 4 consecutive amino acid residues.

The above-mentioned amino acid residues having a large hydrophobicity index are amino acids selected from isoleucine (I), valine (V), leucine (L), phenylalanine (F), cysteine (C), methionine (M), and alanine (A). More preferably, it is a residue.

The fifth modified fibroin is characterized in that one or more amino acid residues in REP are substituted with amino acid residues having a larger hydrophobicity index than in naturally occurring fibroin, and/or one or more amino acid residues in REP In addition to the modification corresponding to the insertion of an amino acid residue with a large hydrophobicity index, one or more amino acid residues are substituted, deleted, inserted, and/or added compared to naturally-derived fibroin. There may also be modifications in the amino acid sequence corresponding to the changes made.

For example, the fifth modified fibroin can be obtained by replacing one or more hydrophilic amino acid residues (for example, amino acid residues with a negative hydrophobicity index) in REP with hydrophobic amino acid residues from the cloned naturally occurring fibroin gene sequence. It can be obtained by substituting a group (for example, an amino acid residue with a positive hydrophobic index) and/or by inserting one or more hydrophobic amino acid residues into REP. In addition, for example, one or more hydrophilic amino acid residues in REP are substituted with hydrophobic amino acid residues from the amino acid sequence of naturally-derived fibroin, and/or one or more hydrophobic amino acid residues in REP It can also be obtained by designing an amino acid sequence corresponding to the insertion of , and chemically synthesizing a nucleic acid encoding the designed amino acid sequence. In either case, one or more hydrophilic amino acid residues in REP are substituted with hydrophobic amino acid residues from the amino acid sequence of naturally occurring fibroin, and/or one or more hydrophobic amino acids in REP In addition to the modification corresponding to the insertion of a residue, the amino acid sequence may be further modified corresponding to the substitution, deletion, insertion, and/or addition of one or more amino acid residues.

The fifth modified fibroin contains a domain sequence represented by formula 1: [(A) _n motif-REP] _m , and a region from the (A) _n motif located on the most C-terminal side to the C-terminus of the above domain sequence. In all REPs included in the sequence obtained by removing the sequence from the above domain sequence, p is the total number of amino acid residues included in the region where the average value of the hydrophobicity index of four consecutive amino acid residues is 2.6 or more, When q is the total number of amino acid residues contained in the sequence obtained by removing the sequence from the (A) _n motif located on the most C-terminal side to the C-terminus of the above domain sequence from the above domain sequence, p/q is 6. .2% or more of the amino acid sequence.

Regarding the hydrophobicity index of amino acid residues, a known index (Hydropathy index: Kyte J, & Doolittle R (1982) “A simple method for displaying the hydropathic character of a p "rotein", J. Mol. Biol., 157, pp. 105-132). Specifically, the hydrophobic index (hydropathy index, hereinafter also referred to as "HI") of each amino acid is as shown in Table 1 below.

The method for calculating p/q will be explained in more detail. For calculation, use formula 1: [(A) _n motif - REP] From the domain sequence represented by _m , remove the sequence from the (A) _n motif located on the C-terminal side to the C-terminus of the domain sequence. (hereinafter referred to as "array A") is used. First, in all REPs included in sequence A, the average value of the hydrophobicity index of four consecutive amino acid residues is calculated. The average value of the hydrophobicity index is determined by dividing the sum of HI of each amino acid residue included in four consecutive amino acid residues by 4 (the number of amino acid residues). The average value of the hydrophobicity index is determined for all four consecutive amino acid residues (each amino acid residue is used to calculate the average value 1 to 4 times). Next, a region where the average value of the hydrophobicity index of four consecutive amino acid residues is 2.6 or more is specified. Even if a certain amino acid residue corresponds to multiple "four consecutive amino acid residues with an average value of hydrophobicity index of 2.6 or more", it may be included as one amino acid residue in the region. become. The total number of amino acid residues contained in the region is p. Further, the total number of amino acid residues included in sequence A is q.

For example, if 20 "4 consecutive amino acid residues with an average hydrophobicity index of 2.6 or more" are extracted (no overlap), the average value of the hydrophobicity index of the 4 consecutive amino acid residues is 2. The region with a value of .6 or more includes 20 consecutive 4 amino acid residues (no overlap), and p is 20×4=80. Also, for example, if two "four consecutive amino acid residues with an average value of hydrophobicity index of 2.6 or more" overlap by one amino acid residue, the hydrophobicity index of the four consecutive amino acid residues The region where the average value of is 2.6 or more will contain 7 amino acid residues (p=2×4−1=7. “−1” is the deduction of overlap.). For example, in the case of the domain sequence shown in Figure 4, there are 7 non-overlapping "4 consecutive amino acid residues with an average hydrophobicity index of 2.6 or more", so p is 7 x 4 = It becomes 28. Further, for example, in the case of the domain sequence shown in FIG. 4, q is 4+50+4+40+4+10+4+20+4+30=170 (not including the (A) _n motif present at the end of the C-terminal side). Next, p/q (%) can be calculated by dividing p by q. In the case of FIG. 4, it is 28/170=16.47%.

In the fifth modified fibroin, p/q is preferably 6.2% or more, more preferably 7% or more, even more preferably 10% or more, and even more preferably 20% or more. It is even more preferable, and even more preferable that it is 30% or more. The upper limit of p/q is not particularly limited, but may be, for example, 45% or less.

The fifth modified fibroin is, for example, one or more hydrophilic amino acid residues in REP (e.g., hydrophobic index substituting a hydrophobic amino acid residue (e.g., an amino acid residue with a positive hydrophobicity index) and/or inserting one or more hydrophobic amino acid residues into the REP. By doing so, it can be obtained by locally modifying the amino acid sequence to include a region with a large hydrophobicity index. Alternatively, for example, it can be obtained by designing an amino acid sequence that satisfies the above p/q condition from the amino acid sequence of naturally occurring fibroin, and chemically synthesizing a nucleic acid encoding the designed amino acid sequence. In either case, one or more amino acid residues in REP have been substituted with amino acid residues with a higher hydrophobic index compared to naturally occurring fibroin, and/or one or more amino acid residues in REP In addition to the modification that corresponds to the insertion of an amino acid residue with a large hydrophobic index, modifications that correspond to the substitution, deletion, insertion, and/or addition of one or more amino acid residues may also be performed. .

Amino acid residues with a large hydrophobic index are not particularly limited, but include isoleucine (I), valine (V), leucine (L), phenylalanine (F), cysteine (C), methionine (M), and alanine (A). ) are preferred, and valine (V), leucine (L) and isoleucine (I) are more preferred.

As a more specific example of the fifth modified fibroin, (5-i) the amino acid sequence shown by SEQ ID NO: 19 (Met-PRT720), SEQ ID NO: 20 (Met-PRT665), or SEQ ID NO: 21 (Met-PRT666), or (5-ii) modified fibroin containing an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 19, SEQ ID NO: 20, or SEQ ID NO: 21.

The modified fibroin (5-i) will be explained. The amino acid sequence shown by SEQ ID NO: 19 is different from the amino acid sequence shown by SEQ ID NO: 7 (Met-PRT410), except for the terminal domain sequence on the C-terminal side, consisting of 3 amino acid residues in every other REP. The amino acid sequence (VLI) is inserted at two positions, some glutamine (Q) residues are replaced with serine (S) residues, and some amino acids on the C-terminal side are deleted. The amino acid sequence shown by SEQ ID NO: 20 is obtained by inserting an amino acid sequence (VLI) consisting of 3 amino acid residues at every other REP in the amino acid sequence shown by SEQ ID NO: 8 (Met-PRT525). be. The amino acid sequence shown by SEQ ID NO: 21 is obtained by inserting an amino acid sequence (VLI) consisting of 3 amino acid residues at two positions in every other REP with respect to the amino acid sequence shown by SEQ ID NO: 8.

The modified fibroin (5-i) may consist of the amino acid sequence shown in SEQ ID NO: 19, SEQ ID NO: 20, or SEQ ID NO: 21.

The modified fibroin (5-ii) contains an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 19, SEQ ID NO: 20, or SEQ ID NO: 21. The modified fibroin (5-ii) is also a protein containing a domain sequence represented by formula 1: [(A) _n motif-REP] _m . The sequence identity is preferably 95% or more.

The modified fibroin of (5-ii) has 90% or more sequence identity with the amino acid sequence shown by SEQ ID NO: 19, SEQ ID NO: 20, or SEQ ID NO: 21, and is located closest to the C-terminus (A) _n Amino acids included in a region where the average value of the hydrophobicity index of four consecutive amino acid residues is 2.6 or more in all REPs included in the domain sequence excluding the sequence from the motif to the C-terminus of the domain sequence. When the total number of residues is p, and the total number of amino acid residues contained in the sequence excluding the sequence from the (A) _n motif to the C-terminus of the domain sequence from the domain sequence located on the most C-terminal side is q. , p/q is preferably 6.2% or more.

The fifth modified fibroin may contain a tag sequence at either or both of the N-terminus and C-terminus.

More specific examples of modified fibroin containing a tag sequence include (5-iii) the amino acid sequence shown by SEQ ID NO: 22 (PRT720), SEQ ID NO: 23 (PRT665), or SEQ ID NO: 24 (PRT666); or (5-iv) ) Modified fibroin containing an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 22, SEQ ID NO: 23, or SEQ ID NO: 24 can be mentioned.

The amino acid sequences shown by SEQ ID NO: 22, SEQ ID NO: 23 and SEQ ID NO: 24 have the amino acid sequence shown by SEQ ID NO: 11 (His tag) at the N-terminus of the amino acid sequences shown by SEQ ID NO: 19, SEQ ID NO: 20 and SEQ ID NO: 21, respectively. (including the hinge arrangement and the hinge arrangement).

The modified fibroin (5-iii) may consist of the amino acid sequence shown in SEQ ID NO: 22, SEQ ID NO: 23, or SEQ ID NO: 24.

The modified fibroin (5-iv) contains an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 22, SEQ ID NO: 23, or SEQ ID NO: 24. The modified fibroin (5-iv) is also a protein containing a domain sequence represented by formula 1: [(A) _n motif-REP] _m . The sequence identity is preferably 95% or more.

The modified fibroin (5-iv) has 90% or more sequence identity with the amino acid sequence shown by SEQ ID NO: 22, SEQ ID NO: 23 or SEQ ID NO: 24, and is located at the most C-terminal side (A) _n Amino acids included in a region where the average value of the hydrophobicity index of four consecutive amino acid residues is 2.6 or more in all REPs included in the domain sequence excluding the sequence from the motif to the C-terminus of the domain sequence. When the total number of residues is p, and the total number of amino acid residues contained in the sequence excluding the sequence from the (A) _n motif to the C-terminus of the domain sequence from the domain sequence located on the most C-terminal side is q. , p/q is preferably 6.2% or more.

The fifth modified fibroin may contain a secretion signal for releasing the protein produced in the recombinant protein production system to the outside of the host. The sequence of the secretion signal can be appropriately set depending on the type of host.

The sixth modified fibroin has an amino acid sequence with a reduced content of glutamine residues compared to naturally occurring fibroin.

The sixth modified fibroin preferably contains at least one motif selected from a GGX motif and a GPGXX motif in the amino acid sequence of REP.

When the sixth modified fibroin contains a GPGXX motif in REP, the GPGXX motif content is usually 1% or more, may be 5% or more, and is preferably 10% or more. The upper limit of the GPGXX motif content is not particularly limited, and may be 50% or less, or 30% or less.

In this specification, "GPGXX motif content" is a value calculated by the following method.
Formula 1: [(A) _n motif-REP] _m or formula 2: [(A) _n motif-REP] _m - ( _A ) fibroin (modified fibroin or naturally In fibroin, the number of GPGXX motifs contained in that region of all REPs contained in the sequence from the (A) _n motif located on the C-terminal side to the C-terminus of the domain sequence is removed from the domain sequence. The total number multiplied by 3 (i.e., equivalent to the total number of G and P in the GPGXX motif) is defined as s, and the sequence from the (A) _n motif located on the C-terminal side to the C-terminus of the domain sequence is calculated from the domain sequence. The GPGXX motif content is calculated as s/t, where t is the total number of amino acid residues in all REPs excluding (A) _n motif.

In calculating the GPGXX motif content rate, the target is the "sequence obtained by removing from the domain sequence the sequence from the (A) _n motif located on the most C-terminal side to the C-terminus of the domain sequence". (A) The sequence from _{the n} motif to the C-terminus of the domain sequence (corresponding to REP) may include sequences that have low correlation with sequences characteristic of fibroin, and m is small. (that is, when the domain sequence is short), this will affect the calculation result of the GPGXX motif content, so this is to eliminate this influence. Note that when a "GPGXX motif" is located at the C-terminus of REP, it is treated as a "GPGXX motif" even if "XX" is, for example, "AA".

FIG. 5 is a schematic diagram showing the domain sequence of modified fibroin. A method for calculating the GPGXX motif content will be specifically described with reference to FIG. 5. First, in the domain sequence of the modified fibroin shown in Figure 5 (which is of the "[(A) _n motif-REP] _m - (A) _n motif" type), all REPs are "located at the most C-terminal side. (A) A sequence obtained by excluding the sequence from _{the n} motif to the C-terminus of the domain sequence from the domain sequence" (sequence shown as "region A" in Figure 5), so it is necessary to calculate s. The number of GPGXX motifs is 7, and s is 7×3=21. Similarly, all REPs are defined as "a sequence obtained by removing from the domain sequence the sequence from the (A) _n motif located on the most C-terminal side to the C-terminus of the domain sequence" (the sequence indicated by "Region A" in Figure 5). ), the total number t of amino acid residues in all REPs, excluding the (A) _n motif, is 50+40+10+20+30=150. Next, s/t (%) can be calculated by dividing s by t, which is 21/150=14.0% for the modified fibroin in FIG.

The sixth modified fibroin preferably has a glutamine residue content of 9% or less, more preferably 7% or less, even more preferably 4% or less, and particularly preferably 0%. .

In this specification, "glutamine residue content" is a value calculated by the following method.
Formula 1: [(A) _n motif-REP] _m or formula 2: [(A) _n motif-REP] _m - ( _A ) fibroin (modified fibroin or naturally In fibroin), everything contained in the sequence (corresponding to "region A" in Figure 5) obtained by excluding the sequence from the (A) _n motif located on the C-terminal side to the C-terminus of the domain sequence from the domain sequence (sequence corresponding to "region A" in Figure 5). In REP, the total number of glutamine residues included in that region is u, and the sequence from the (A) _n motif located on the most C-terminal side to the C-terminus of the domain sequence is removed from the domain sequence, and then (A) _n The glutamine residue content is calculated as u/t, where t is the total number of amino acid residues in all REPs excluding motifs. In calculating the glutamine residue content, we target "sequences obtained by excluding the sequence from the (A) _n motif located on the C-terminal side to the C-terminus of the domain sequence from the domain sequence" due to the above-mentioned reasons and The same is true.

The sixth modified fibroin corresponds to a domain sequence in which one or more glutamine residues in REP are deleted or substituted with other amino acid residues compared to naturally occurring fibroin. It may have an amino acid sequence.

"Other amino acid residues" may be any amino acid residues other than glutamine residues, but are preferably amino acid residues with a larger hydrophobicity index than glutamine residues. The hydrophobicity index of amino acid residues is as shown in Table 1.

As shown in Table 1, amino acid residues with a higher hydrophobic index than glutamine residues include isoleucine (I), valine (V), leucine (L), phenylalanine (F), cysteine (C), and methionine (M ) Amino acid residues selected from alanine (A), glycine (G), threonine (T), serine (S), tryptophan (W), tyrosine (Y), proline (P) and histidine (H) may be mentioned. can. Among these, amino acid residues selected from isoleucine (I), valine (V), leucine (L), phenylalanine (F), cysteine (C), methionine (M) and alanine (A) are more preferred. , isoleucine (I), valine (V), leucine (L) and phenylalanine (F).

In the sixth modified fibroin, the degree of hydrophobicity of REP is preferably -0.8 or more, more preferably -0.7 or more, still more preferably 0 or more, and 0.3 or more. It is even more preferable that it is, and it is particularly preferable that it is 0.4 or more. The upper limit of the degree of hydrophobicity of REP is not particularly limited, and may be 1.0 or less, or may be 0.7 or less.

In this specification, "hydrophobicity of REP" is a value calculated by the following method.
Formula 1: [(A) _n motif-REP] _m or formula 2: [(A) _n motif-REP] _m - ( _A ) fibroin (modified fibroin or naturally In fibroin), everything contained in the sequence (corresponding to "region A" in Figure 5) obtained by excluding the sequence from the (A) _n motif located on the C-terminal side to the C-terminus of the domain sequence from the domain sequence (sequence corresponding to "region A" in Figure 5). In REP, the sum of the hydrophobicity indices of each amino acid residue in that region is v, and the sequence from the (A) _n motif located on the most C-terminal side to the C-terminus of the domain sequence is removed from the domain sequence, and further ( A) The hydrophobicity of REP is calculated as v/t, where t is the total number of amino acid residues in all REPs excluding the _n motif. In calculating the degree of hydrophobicity of REP, we target "sequences obtained by excluding the sequence from the (A) _n motif located on the C-terminal side to the C-terminus of the domain sequence from the domain sequence" due to the above-mentioned reasons and The same is true.

The sixth modified fibroin has a domain sequence in which one or more glutamine residues in REP are deleted compared to naturally occurring fibroin, and/or one or more glutamine residues in REP In addition to modifications corresponding to the substitution of other amino acid residues, there may also be modifications of the amino acid sequence corresponding to substitutions, deletions, insertions, and/or additions of one or more amino acid residues. .

The sixth modified fibroin can be produced by, for example, deleting one or more glutamine residues in REP from the cloned naturally-derived fibroin gene sequence, and/or replacing one or more glutamine residues in REP with another one. can be obtained by substituting the amino acid residue of In addition, for example, one or more glutamine residues in REP have been deleted from the amino acid sequence of naturally-derived fibroin, and/or one or more glutamine residues in REP have been replaced with other amino acid residues. It can also be obtained by designing a corresponding amino acid sequence and chemically synthesizing a nucleic acid encoding the designed amino acid sequence.

More specific examples of the sixth modified fibroin include (6-i) SEQ ID NO: 25 (Met-PRT888), SEQ ID NO: 26 (Met-PRT965), SEQ ID NO: 27 (Met-PRT889), SEQ ID NO: 28 (Met -PRT916), SEQ ID NO: 29 (Met-PRT918), SEQ ID NO: 30 (Met-PRT699), SEQ ID NO: 31 (Met-PRT698), SEQ ID NO: 32 (Met-PRT966), SEQ ID NO: 41 (Met-PRT917) or sequence Modified fibroin comprising the amino acid sequence shown by number 42 (Met-PRT1028), or (6-ii) SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , SEQ ID NO: 32, SEQ ID NO: 41, or SEQ ID NO: 42, and modified fibroin containing an amino acid sequence having 90% or more sequence identity.

The modified fibroin (6-i) will be explained. The amino acid sequence shown by SEQ ID NO: 25 is obtained by replacing all QQ in the amino acid sequence shown by SEQ ID NO: 7 (Met-PRT410) with VL. The amino acid sequence shown by SEQ ID NO: 26 is obtained by replacing all QQ in the amino acid sequence shown by SEQ ID NO: 7 with TS, and replacing the remaining Q with A. The amino acid sequence shown by SEQ ID NO: 27 is obtained by replacing all QQ in the amino acid sequence shown by SEQ ID NO: 7 with VL, and replacing the remaining Q with I. The amino acid sequence shown by SEQ ID NO: 28 is obtained by replacing all QQ in the amino acid sequence shown by SEQ ID NO: 7 with VI, and replacing the remaining Q with L. The amino acid sequence shown by SEQ ID NO: 29 is obtained by replacing all QQ in the amino acid sequence shown by SEQ ID NO: 7 with VF, and replacing the remaining Q with I.

The amino acid sequence shown by SEQ ID NO: 30 is obtained by replacing all QQ in the amino acid sequence shown by SEQ ID NO: 8 (Met-PRT525) with VL. The amino acid sequence shown by SEQ ID NO: 31 is obtained by replacing all QQ in the amino acid sequence shown by SEQ ID NO: 8 with VL, and replacing the remaining Q with I.

The amino acid sequence shown by SEQ ID NO: 32 is obtained by replacing all QQ with VF in the sequence in which the 20 domain sequence regions present in the amino acid sequence shown by SEQ ID NO: 7 (Met-PRT410) are repeated twice, And the remaining Q is replaced with I.

The amino acid sequence shown by SEQ ID NO: 41 (Met-PRT917) is obtained by replacing all QQ in the amino acid sequence shown by SEQ ID NO: 7 with LI, and replacing the remaining Q with V. The amino acid sequence shown by SEQ ID NO: 42 (Met-PRT1028) is obtained by replacing all QQ in the amino acid sequence shown by SEQ ID NO: 7 with IF, and replacing the remaining Q with T.

The amino acid sequences shown by SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32, SEQ ID NO: 41 and SEQ ID NO: 42 all contain glutamine residues. The group content is below 9% (Table 2).

The modified fibroin of (6-i) is SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32, SEQ ID NO: 41 or SEQ ID NO: 42. It may consist of the amino acid sequence shown.

The modified fibroin of (6-ii) is SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32, SEQ ID NO: 41 or SEQ ID NO: 42. It contains an amino acid sequence having 90% or more sequence identity with the indicated amino acid sequence. The modified fibroin of (6-ii) also has a domain represented by Formula 1: [(A) _n motif-REP] _m or Formula 2: [(A) _n motif-REP] _m - (A) _n motif. It is a protein that contains a sequence. The sequence identity is preferably 95% or more.

The modified fibroin (6-ii) preferably has a glutamine residue content of 9% or less. Furthermore, the modified fibroin (6-ii) preferably has a GPGXX motif content of 10% or more.

The sixth modified fibroin may contain a tag sequence at either or both of the N-terminus and C-terminus. This makes it possible to isolate, immobilize, detect, visualize, etc. the modified fibroin.

More specific examples of modified fibroin containing tag sequences include (6-iii) SEQ ID NO: 33 (PRT888), SEQ ID NO: 34 (PRT965), SEQ ID NO: 35 (PRT889), SEQ ID NO: 36 (PRT916), SEQ ID NO: 37 (PRT918), SEQ ID NO: 38 (PRT699), SEQ ID NO: 39 (PRT698), SEQ ID NO: 40 (PRT966), SEQ ID NO: 43 (PRT917) or SEQ ID NO: 44 (PRT1028), or ( 6-iv) Amino acid sequence shown by SEQ ID NO: 33, SEQ ID NO: 34, SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40, SEQ ID NO: 43 or SEQ ID NO: 44 and 90 Mention may be made of modified fibroin comprising amino acid sequences having % or more sequence identity.

The amino acid sequences shown by SEQ ID NO: 33, SEQ ID NO: 34, SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40, SEQ ID NO: 43 and SEQ ID NO: 44 are SEQ ID NO: 25, respectively. , SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32, SEQ ID NO: 41, and SEQ ID NO: 42. The amino acid sequence (including His tag sequence and hinge sequence) is added. Since the tag sequence was only added to the N-terminus, there was no change in the glutamine residue content, and SEQ ID NO: 33, SEQ ID NO: 34, SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39 , SEQ ID NO: 40, SEQ ID NO: 43, and SEQ ID NO: 44 all have a glutamine residue content of 9% or less (Table 3).

The modified fibroin of (6-iii) is SEQ ID NO: 33, SEQ ID NO: 34, SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40, SEQ ID NO: 43 or SEQ ID NO: 44. It may consist of the amino acid sequence shown.

The modified fibroin of (6-iv) is SEQ ID NO: 33, SEQ ID NO: 34, SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40, SEQ ID NO: 43 or SEQ ID NO: 44. It contains an amino acid sequence having 90% or more sequence identity with the indicated amino acid sequence. The modified fibroin of (6-iv) also has a domain represented by formula 1: [(A) _n motif-REP] _m or formula 2: [(A) _n motif-REP] _m - (A) _n motif. It is a protein that contains a sequence. The sequence identity is preferably 95% or more.

The modified fibroin (6-iv) preferably has a glutamine residue content of 9% or less. Furthermore, the modified fibroin (6-iv) preferably has a GPGXX motif content of 10% or more.

The sixth modified fibroin may contain a secretion signal for releasing the protein produced in the recombinant protein production system to the outside of the host. The sequence of the secretion signal can be appropriately set depending on the type of host.

The modified fibroin has at least two or more of the characteristics possessed by the first modified fibroin, the second modified fibroin, the third modified fibroin, the fourth modified fibroin, the fifth modified fibroin, and the sixth modified fibroin. It may also be a modified fibroin that has the following characteristics.

The modified fibroin is preferably a hydrophobic modified fibroin because it has better heat retention properties. As used herein, "hydrophobically modified fibroin" refers to the value obtained by calculating the sum of the hydrophobicity index (HI) of all amino acid residues constituting the modified fibroin, and then dividing the sum by the total number of amino acid residues. (Average HI) of more than 0. The average value of the hydrophobic index (average HI) of the modified fibroin is preferably 0.5 or more, more preferably 0.6 or more. The average value of the hydrophobicity index (average HI) of the modified fibroin may be, for example, 1.2 or less, or 0.9 or less. The hydrophobicity index is as shown in Table 1. Furthermore, modified fibroin having an average HI of 0 or less is sometimes referred to as hydrophilic modified fibroin.

Examples of the hydrophobically modified fibroin include the amino acid sequences shown in SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32, SEQ ID NO: 33, or SEQ ID NO: 43, SEQ ID NO: 35, Examples include modified fibroin containing the amino acid sequence shown by SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40, SEQ ID NO: 41, or SEQ ID NO: 44.

Examples of the hydrophilic modified fibroin include the amino acid sequence shown by SEQ ID NO: 4, the amino acid sequence shown by SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, SEQ ID NO: 13, SEQ ID NO: 11, SEQ ID NO: 14. or the amino acid sequence shown by SEQ ID NO: 15, the amino acid sequence shown by SEQ ID NO: 18, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, the amino acid sequence shown by SEQ ID NO: 17, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15. Examples include modified fibroin containing the amino acid sequence shown in SEQ ID NO: 19, SEQ ID NO: 20, or SEQ ID NO: 21.

(Method for producing modified fibroin)
The modified fibroin according to any of the above embodiments can be used, for example, in a host transformed with an expression vector having a nucleic acid sequence encoding the modified fibroin and one or more regulatory sequences operably linked to the nucleic acid sequence. can be produced by expressing the nucleic acid.

The method for producing a nucleic acid encoding modified fibroin is not particularly limited. For example, the nucleic acid is produced by using a gene encoding natural fibroin, amplifying it by polymerase chain reaction (PCR), cloning it, modifying it by genetic engineering techniques, or chemically synthesizing it. can do. The method of chemically synthesizing nucleic acids is also not particularly limited, and for example, it can be synthesized using AKTA oligopilot plus 10/100 (GE Healthcare Japan Co., Ltd.) based on the amino acid sequence information of fibroin obtained from the NCBI web database. Genes can be chemically synthesized by linking automatically synthesized oligonucleotides using PCR or the like. At this time, in order to facilitate purification and/or confirmation of modified fibroin, a nucleic acid encoding modified fibroin consisting of an amino acid sequence with an amino acid sequence consisting of a start codon and a His10 tag added to the N-terminus of the above amino acid sequence was synthesized. You may.

The regulatory sequence is a sequence (eg, promoter, enhancer, ribosome binding sequence, transcription termination sequence, etc.) that controls the expression of modified fibroin in the host, and can be appropriately selected depending on the type of host. As the promoter, an inducible promoter that functions in the host cell and can induce expression of the modified fibroin may be used. An inducible promoter is a promoter whose transcription can be controlled by the presence of an inducer (expression inducer), the absence of a repressor molecule, or a physical factor such as an increase or decrease in temperature, osmotic pressure, or pH value.

The type of expression vector can be appropriately selected depending on the type of host, such as a plasmid vector, a virus vector, a cosmid vector, a fosmid vector, or an artificial chromosome vector. As the expression vector, one that is capable of autonomous replication in the host cell or can be integrated into the chromosome of the host, and contains a promoter at a position where the nucleic acid encoding the modified fibroin can be transcribed is preferably used.

As the host, any of prokaryotes and eukaryotes such as yeast, filamentous fungi, insect cells, animal cells, and plant cells can be suitably used.

Preferred examples of prokaryotic hosts include bacteria belonging to the genus Escherichia, Brevibacillus, Serratia, Bacillus, Microbacterium, Brevibacterium, Corynebacterium, Pseudomonas, and the like. Examples of microorganisms belonging to the genus Escherichia include Escherichia coli. Examples of microorganisms belonging to the genus Brevibacillus include Brevibacillus agri. Examples of microorganisms belonging to the genus Serratia include Serratia liquefaciens. Examples of microorganisms belonging to the genus Bacillus include Bacillus subtilis. Examples of microorganisms belonging to the genus Microbacterium include Microbacterium ammoniaphyllum. Examples of microorganisms belonging to the genus Brevibacterium include Brevibacterium divaricatum. Examples of microorganisms belonging to the genus Corynebacterium include Corynebacterium ammoniagenes. Examples of microorganisms belonging to the genus Pseudomonas include Pseudomonas putida.

When a prokaryote is used as a host, vectors for introducing a nucleic acid encoding modified fibroin include, for example, pBTrp2 (manufactured by Boehringer Mannheim), pGEX (manufactured by Pharmacia), pUC18, pBluescript II, pSupex, pET22b, pCold, pUB110, Examples include pNCO2 (Japanese Patent Application Laid-open No. 2002-238569).

Eukaryotic hosts include, for example, yeast and filamentous fungi (molds, etc.). Examples of yeast include yeasts belonging to the genus Saccharomyces, Pichia, Schizosaccharomyces, and the like. Examples of filamentous fungi include filamentous fungi belonging to the genus Aspergillus, Penicillium, Trichoderma, and the like.

When a eukaryote is used as a host, examples of vectors for introducing a nucleic acid encoding modified fibroin include YEP13 (ATCC 37115) and YEp24 (ATCC 37051). Any method for introducing DNA into the host cells can be used as a method for introducing the expression vector into the host cells. For example, a method using calcium ions [Proc. Natl. Acad. Sci. USA, 69, 2110 (1972)], electroporation method, spheroplast method, protoplast method, lithium acetate method, competent method, and the like.

In addition to direct expression, methods for expressing nucleic acids by hosts transformed with expression vectors include secretory production, fusion protein expression, etc. according to the methods described in Molecular Cloning, 2nd edition. .

Modified fibroin can be produced, for example, by culturing a host transformed with an expression vector in a culture medium, producing and accumulating the modified fibroin in the culture medium, and collecting it from the culture medium. The host can be cultured in a culture medium according to a method commonly used for culturing hosts.

When the host is a prokaryote such as Escherichia coli or a eukaryote such as yeast, the culture medium contains a carbon source, nitrogen source, inorganic salts, etc. that can be assimilated by the host, and allows efficient culture of the host. Either a natural medium or a synthetic medium may be used.

The carbon source may be anything that can be assimilated by the transformed microorganisms, such as carbohydrates such as glucose, fructose, sucrose, molasses containing these, starch and starch hydrolysates, and acetic acid and propionic acid. Organic acids and alcohols such as ethanol and propanol can be used. Examples of nitrogen sources include ammonium salts of inorganic or organic acids such as ammonia, ammonium chloride, ammonium sulfate, ammonium acetate and ammonium phosphate, other nitrogen-containing compounds, as well as peptone, meat extract, yeast extract, corn steep liquor, Casein hydrolysates, soybean meal and soybean meal hydrolysates, various fermented microbial cells, and digested products thereof can be used. As the inorganic salts, for example, potassium phosphate, dipotassium phosphate, magnesium phosphate, magnesium sulfate, sodium chloride, ferrous sulfate, manganese sulfate, copper sulfate, and calcium carbonate can be used.

Culture of prokaryotes such as Escherichia coli or eukaryotes such as yeast can be carried out under aerobic conditions such as shaking culture or deep aeration agitation culture. The culture temperature is, for example, 15 to 40°C. The culture time is usually 16 hours to 7 days. The pH of the culture medium during culture is preferably maintained at 3.0 to 9.0. The pH of the culture medium can be adjusted using inorganic acids, organic acids, alkaline solutions, urea, calcium carbonate, ammonia, and the like.

Furthermore, during culture, antibiotics such as ampicillin and tetracycline may be added to the culture medium as necessary. When culturing a microorganism transformed with an expression vector using an inducible promoter as a promoter, an inducer may be added to the medium as necessary. For example, isopropyl-β-D-thiogalactopyranoside is used when culturing a microorganism transformed with an expression vector using the lac promoter, and indole acrylate is used when culturing a microorganism transformed with an expression vector using the trp promoter. An acid or the like may be added to the medium.

The expressed modified fibroin can be isolated and purified by commonly used methods. For example, when the modified fibroin is expressed in a dissolved state in cells, after the completion of culture, the host cells are collected by centrifugation, suspended in an aqueous buffer, and then processed using an ultrasonicator, French press, or Manton. Host cells are disrupted using a Gaulin homogenizer, Dynomill, etc. to obtain a cell-free extract. From the supernatant obtained by centrifuging the cell-free extract, methods commonly used for isolation and purification of proteins, such as solvent extraction, salting out with ammonium sulfate, desalting, and organic solvents. precipitation method, diethylaminoethyl (DEAE)-Sepharose, anion exchange chromatography method using resins such as DIAION HPA-75 (manufactured by Mitsubishi Kasei Corporation), and positive chromatography method using resins such as S-Sepharose FF (manufactured by Pharmacia Corporation). Ion exchange chromatography, hydrophobic chromatography using resins such as butyl Sepharose and phenyl Sepharose, gel filtration using molecular sieves, affinity chromatography, chromatofocusing, and electrophoresis such as isoelectric focusing. A purified sample can be obtained by using these methods alone or in combination.

In addition, when the modified fibroin is expressed by forming an insoluble body within the cells, the host cells are similarly collected, disrupted, and centrifuged to recover the insoluble body of the modified fibroin as a precipitate fraction. The recovered insoluble modified fibroin can be solubilized with a protein denaturing agent. After this operation, a purified sample of modified fibroin can be obtained by the same isolation and purification method as above. When the modified fibroin is secreted extracellularly, the modified fibroin can be recovered from the culture supernatant. That is, a culture supernatant is obtained by processing a culture using techniques such as centrifugation, and a purified sample can be obtained from the culture supernatant by using the same isolation and purification method as described above.

(Heat retention agent)
The heat retention agent according to the present embodiment may contain one type of modified fibroin alone, or may contain a combination of two or more types of modified fibroin.

The heat retention agent according to the present embodiment may have a heat retention index of 0.20 or more determined according to formula A below.
Formula A: Heat retention index = heat retention rate (%) / basis weight of sample (g/m ² )
Here, in this specification, the heat retention rate means the heat retention rate measured by the dry contact method using a Thermolab II type tester (under wind conditions of 30 cm/sec), and is measured by the method described in the Examples below. is the value to be used.

The heat retention index of the heat retention agent according to the present embodiment may be 0.22 or more, 0.24 or more, 0.26 or more, or 0.28 or more. , may be 0.30 or more, and may be 0.32 or more. The upper limit of the heat retention index is not particularly limited, but may be, for example, 0.60 or less, or 0.40 or less.

The heat retention agent according to the present embodiment may further contain other additives (components other than the active ingredient) depending on its form, use, etc. Examples of additives include plasticizers, leveling agents, crosslinking agents, crystal nucleating agents, antioxidants, ultraviolet absorbers, colorants, fillers, and synthetic resins. The content of the additive may be 50 parts by mass or less based on 100 parts by mass of the total heat retention agent.

The heat retention agent according to the present embodiment may be in any form, for example, powder, paste, or liquid (eg, suspension, solution). The heat retention agent according to the present embodiment may also be in the form of, for example, fibers, films, gels, porous bodies, particles, or the like. The form of the heat retention agent according to the present embodiment may be appropriately set depending on the object to which heat retention is to be imparted (the article to which heat retention is imparted) and its use.

Since the heat retention agent according to the present embodiment contains modified fibroin as a main component, it can be molded into any of the above-mentioned forms. The molded body may be one formed by molding the modified fibroin itself, or may be one formed by combining the modified fibroin with another material.

When preparing the heat retention agent according to the present embodiment in powder form, for example, the protein obtained by the above-mentioned method for producing modified fibroin may be dried and made into powder form. The protein powder may contain other additives as necessary.

When preparing the heat retention agent according to the present embodiment in a liquid form (for example, a solution), for example, the modified fibroin obtained by the above-mentioned method for producing modified fibroin is dissolved in a solvent that can dissolve the modified fibroin. solution). The modified fibroin solution may contain other additives as necessary. Examples of solvents that can dissolve modified fibroin include dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), formic acid, and hexafluoroisopropanol (HFIP). An inorganic salt may be added to the solvent as a solubility promoter.

When preparing the heat retention agent according to the present embodiment in the form of fibers, for example, the above-mentioned modified fibroin solution is used as a dope solution, and the yarn is spun by a known spinning method such as wet spinning, dry spinning, dry-wet spinning, or melt spinning. It may also be made into fibers (modified fibroin fibers). The form of the fiber may be a single yarn, a composite yarn such as a blended yarn, mixed yarn, mixed yarn, interwoven yarn, twisted yarn, covering yarn, or nonwoven fabric. good.

The modified fibroin fibers may be short fibers or long fibers. Further, the modified fibroin fiber may be a modified fibroin fiber alone or may be combined with other fibers. That is, a single yarn made only of modified fibroin fibers, a composite yarn made of a combination of modified fibroin fibers and other fibers, each alone, or a combination thereof may be used. The single yarn and the composite yarn may be spun yarns made of short fibers twisted together, or filament yarns made of long fibers twisted together or not twisted together. In addition, modified fibroin fibers, whether short fibers or long fibers, can be used as fibers without being processed into threads, either alone or in combination with other fibers. Examples of other fibers include synthetic fibers such as nylon and polyester, recycled fibers such as cupro and rayon, and natural fibers such as cotton and linen. When used in combination with other fibers, the content of modified fibroin fibers is preferably 20% by mass or more, more preferably 30% by mass or more, and 40% by mass based on the total amount of fibers. It is more preferably at least 50% by mass, and even more preferably at least 50% by mass.

When the heat retention agent according to the present embodiment is prepared in the form of a film, gel, porous body, particle, etc., for example, JP-A No. 2009-505668, JP-A No. 2009-505668, and Japanese Patent No. 5678283. , Japanese Patent No. 4,638,735, and the like.

[Method of imparting heat retention to articles]
The method of imparting heat retention to an article according to the present embodiment includes a step of causing the article to contain modified fibroin. The modified fibroin according to the present invention has excellent heat retention properties, and therefore, by incorporating it into an article, it can impart heat retention properties to the article.

There are no particular restrictions on the article as long as it provides heat retention. Specifically, woven fabrics, knitted fabrics, non-woven fabrics, cotton, sponges, films, resins, composite materials (the form of the heat retention agent according to this embodiment does not matter), and various articles made using them, etc. can be mentioned.

The step of containing modified fibroin may be a step of containing modified fibroin by containing the above-mentioned heat retention agent according to the present invention. There is no particular restriction on the method of incorporating modified fibroin, and it may be a method of mixing modified fibroin into the material (raw material), or by adding the heat retention agent prepared in the form of the molded article described above to another material (molded material). It may also be a method of forming an article by combining it with a body (such as a body). Alternatively, a method may be used in which an article (molded body) is formed by molding the modified fibroin itself (which may contain other additives as necessary).

The content of modified fibroin in the article is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 50% by mass, based on the total amount of the article. It is even more preferable that it is the above. The upper limit of the content of modified fibroin may be 100% by mass or 90% by mass or less based on the total amount of the article. By adjusting the content of modified fibroin in the article, the heat retention properties of the article can be controlled. That is, since the modified fibroin according to the present invention has excellent heat retention properties, as the content of modified fibroin in the article is increased, the heat retention properties of the article can be further increased.

Hereinafter, the present invention will be explained more specifically based on Examples and the like. However, the present invention is not limited to the following examples.

[Manufacture of modified fibroin]
(1) Preparation of expression vectors Modified fibroin (PRT966) having the amino acid sequence shown by SEQ ID NO: 40 and modified fibroin (PRT799) having the amino acid sequence shown by SEQ ID NO: 15 were designed. A nucleic acid encoding the designed modified fibroin was synthesized. An NdeI site was added to the 5' end of the nucleic acid, and an EcoRI site was added downstream of the stop codon. This nucleic acid was cloned into a cloning vector (pUC118). Thereafter, the same nucleic acid was excised by restriction enzyme treatment with NdeI and EcoRI, and then recombined with the protein expression vector pET-22b(+) to obtain an expression vector.

(2) Protein expression Escherichia coli BLR (DE3) was transformed with the obtained expression vector. The transformed E. coli was cultured in 2 mL of LB medium containing ampicillin for 15 hours. The culture solution was added to 100 mL of seed culture medium (Table 4) containing ampicillin so that the OD ₆₀₀ was 0.005. The culture solution temperature was maintained at 30° C., and flask culture was performed until OD ₆₀₀ reached 5 (about 15 hours) to obtain a seed culture solution.

The seed culture solution was added to a jar fermenter supplemented with 500 mL of production medium (Table 5) so that the OD ₆₀₀ was 0.05. Culture was carried out by keeping the culture solution temperature at 37° C. and controlling the pH to be constant at 6.9. Further, the dissolved oxygen concentration in the culture solution was maintained at 20% of the dissolved oxygen saturation concentration.

Immediately after the glucose in the production medium was completely consumed, feed solution (glucose 455 g/1 L, Yeast Extract 120 g/1 L) was added at a rate of 1 mL/min. Culture was carried out by keeping the culture solution temperature at 37° C. and controlling the pH to be constant at 6.9. Further, the dissolved oxygen concentration in the culture solution was maintained at 20% of the dissolved oxygen saturation concentration, and culture was performed for 20 hours. Thereafter, 1M isopropyl-β-thiogalactopyranoside (IPTG) was added to the culture solution to a final concentration of 1mM to induce expression of the modified fibroin. After 20 hours had passed after the addition of IPTG, the culture solution was centrifuged and the bacterial cells were collected. Perform SDS-PAGE using the bacterial cells prepared from the culture medium before and after addition of IPTG, and confirm the expression of the desired modified fibroin by the appearance of a band of the desired modified fibroin size that is dependent on the addition of IPTG. did.

(3) Protein purification The bacterial cells collected 2 hours after adding IPTG were washed with 20mM Tris-HCl buffer (pH 7.4). The washed cells were suspended in 20 mM Tris-HCl buffer (pH 7.4) containing about 1 mM PMSF, and the cells were disrupted using a high-pressure homogenizer (manufactured by GEA Niro Soavi). The crushed cells were centrifuged to obtain a precipitate. The resulting precipitate was washed with 20mM Tris-HCl buffer (pH 7.4) until high purity. The washed precipitate was suspended in 8M guanidine buffer (8M guanidine hydrochloride, 10mM sodium dihydrogen phosphate, 20mM NaCl, 1mM Tris-HCl, pH 7.0) to a concentration of 100mg/mL and incubated at 60°C. The mixture was stirred with a stirrer for 30 minutes to dissolve the mixture. After dissolution, dialysis was performed against water using a dialysis tube (cellulose tube 36/32 manufactured by Sanko Junyaku Co., Ltd.). Modified fibroin (PRT966 and PRT799) was obtained by collecting the white aggregated protein obtained after dialysis by centrifugation, removing water with a freeze dryer, and collecting freeze-dried powder.

PRT966 has hydrophobicity and the average value of the hydrophobicity index (average HI) is a value exceeding 0, and PRT799 has hydrophilicity and the average value of the hydrophobicity index (average HI) is a value less than 0. Met.

[Manufacture of protein fiber]
Prepare dimethyl sulfoxide (DMSO) in which LiCl is dissolved to a concentration of 4.0% by mass as a solvent, add freeze-dried powder of modified fibroin to a concentration of 24% by mass, and use a shaker to dissolve the lyophilized powder of modified fibroin. It was allowed to dissolve for 3 hours. Thereafter, insoluble matters and bubbles were removed to obtain a modified fibroin solution (spinning stock solution).

The prepared spinning stock solution was filtered at 60°C through a metal filter with an opening of 5 μm, then left to stand in a 30 mL stainless steel syringe to defoam, and then coagulated with 100% methanol from a solid nozzle with a needle diameter of 0.2 mm. I vomited it into the bathtub. The discharge temperature was 60°C. After coagulation, the obtained yarn was wound up and naturally dried to obtain a modified fibroin fiber (raw material fiber).

For comparison, commercially available wool fibers, silk fibers, cotton fibers, rayon fibers, and polyester fibers were prepared as raw material fibers.

[Manufacture of knitted fabric]
Using each raw material fiber, a knitted fabric was manufactured by flat knitting using a flat knitting machine. The knitted fabric using PRT966 fiber as the raw material fiber had a count of 30 Nm, number of twists: 1, gauge number: 18 GG, and basis weight: 90.1 g/m ² . The knitted fabric using PRT799 fiber as the raw material fiber had a count of 30 Nm, number of twists: 1, gauge number GG: 16, and basis weight: 111.0 g/m ² . The thickness and gauge number of the knitted fabrics using other raw material fibers were adjusted so that they had almost the same cover factor as the knitted fabrics using PRT966 fibers and PRT799 fibers. Specifically, it is as follows.
Wool count: 30Nm, number of twists: 2, number of gauges: 14GG, basis weight: 242.6g/m ²
Silk count: 60Nm, number of twists: 2, number of gauge: 14GG, basis weight: 225.2g/m ²
Cotton count: 34Nm, number of twists: 2, number of gauge: 14GG, basis weight: 194.1g/m ²
Rayon count: 38Nm, number of twists: 1, number of gauges: 14GG, basis weight: 181.8g/m ²
Polyester count: 60Nm, number of twists: 1, number of gauges: 14GG, basis weight: 184.7g/ ^m2

[Heat retention test]
Heat retention was evaluated using a KES-F7 Thermolab II tester manufactured by Kato Tech Co., Ltd. using a dry contact method (a method assuming direct contact between skin and clothing in a dry state). One piece of knitted fabric cut to 20 cm x 20 cm was used as a test piece (sample). The test piece was set on a hot plate set at a constant temperature (30° C.), and the amount of heat (a) dissipated through the test piece was determined under conditions of a wind speed of 30 cm/sec in the wind tunnel. The amount of heat dissipated (b) was determined under the same conditions as above without setting the test piece, and the heat retention rate (%) was calculated according to the following formula.
Heat retention rate (%) = (1-a/b) x 100

From the measurement results, a heat retention index was determined according to formula A below.
Formula A: Heat retention index = heat retention rate (%) / basis weight of sample (g/m ² )

Table 6 shows the calculation results of the heat retention index. The higher the heat retention index, the better the material can be evaluated for heat retention.

As shown in Table 6, it can be seen that the modified fibroin (PRT966 and PRT799) has a higher heat retention index and is superior in heat retention than existing materials. Therefore, by manufacturing an article using modified fibroin alone or by mixing modified fibroin with other materials, an article having excellent heat retention properties can be obtained.

Claims (6)

Contains modified fibroin as an active ingredient,
The modified fibroin contains modified fibroin with an average value of hydrophobicity index (average HI) of more than 0,
A heat retention agent in the form of fibers . The heat retention agent according to claim 1, wherein the modified fibroin includes modified spider silk fibroin. Contains modified fibroin as an active ingredient,
the modified fibroin comprises modified spider silk fibroin,
The modified spider silk fibroin has the formula 1: [(A) _n motif-REP] _m , or the formula 2: [(A) _n motif-REP] _m - (A) _n (wherein in formula 1 or formula 2) , (A) _n motif indicates an amino acid sequence composed of 2 to 27 amino acid residues, and (A) the number of alanine residues is 40% or more of the total number of amino acid residues in _n motif. REP is 10 Indicates an amino acid sequence consisting of ~200 amino acid residues. m represents an integer from 8 to 300. Multiple (A) _n motifs may have the same or different amino acid sequences. Multiple exist. The REPs may have the same amino acid sequence or may have different amino acid sequences.'' A heat retention agent. The heat retention agent according to claim 3 , which is in the form of fibers. A method of imparting heat retention to an article, the method comprising:
comprising the step of containing modified fibroin in the form of fibers in the article ,
The method , wherein the modified fibroin has a hydrophobicity index average value (average HI) of more than 0 . A method of imparting heat retention to an article, the method comprising:
comprising a step of causing the article to contain modified fibroin,
the modified fibroin comprises modified spider silk fibroin,
The modified spider silk fibroin has the formula 1: [(A) _n Motif-REP] _m , or Formula 2: [(A) _n Motif-REP] _m -(A) _n (Here, in formula 1 or formula 2, (A) _n The motif represents an amino acid sequence consisting of 2 to 27 amino acid residues, and (A) _n The number of alanine residues is 40% or more of the total number of amino acid residues in the motif. REP indicates an amino acid sequence composed of 10 to 200 amino acid residues. m represents an integer from 8 to 300. There are multiple (A) _n The motifs may have the same or different amino acid sequences. A plurality of REPs may have the same or different amino acid sequences. ”, the method comprises an amino acid sequence represented by “.

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