CN117126255A

CN117126255A - Lantibiotic Bicereucin mutants and uses thereof

Info

Publication number: CN117126255A
Application number: CN202210545988.4A
Authority: CN
Inventors: 霍刘杰; 樊国庆
Original assignee: SUZHOU RESEARCH INSTITUTE SHANDONG UNIVERSITY; Shandong University
Current assignee: SUZHOU RESEARCH INSTITUTE SHANDONG UNIVERSITY; Shandong University
Priority date: 2022-05-19
Filing date: 2022-05-19
Publication date: 2023-11-28

Abstract

The invention belongs to the technical field of pharmaceutical chemistry, and particularly relates to a bi-component lantibiotic Bicereucin mutant and application thereof. A variant of the lantibiotic antibiotic Bicereucin, which variant is a mutation of D-Ala at position 17 or position 30 of Bsj alpha to L-Ala; the 19 th D-Abu or 31 st D-Ala of Bsjβ is mutated into any one of L-Ala, wherein the amino acid sequence of Bsjα is shown as SEQ ID No.3, and the amino acid sequence of Bsjβ is shown as SEQ ID No. 4. The invention provides novel lantibiotic antibiotic Bicereucin mutants having significantly reduced hemolytic activity relative to the wild type; meanwhile, experiments prove that the biological functions of Bsj alpha, bsj beta and mutants thereof are verified, and the mutants of the Bsj alpha, bsj beta and mutants thereof have synergistic effect with the other wild type, so that the Bsj alpha, bsj beta and mutants have excellent antibacterial activity and low hemolytic property, and the optimal antibacterial activity is shown in a molar ratio of 2:1, thereby providing a material basis for preparing the lantibiotic antibiotics Bicerucin.

Description

Lantibiotic Bicereucin mutants and uses thereof

Technical Field

The invention belongs to the technical field of pharmaceutical chemistry, and particularly relates to a lantibiotic Bicereucin mutant and application thereof.

Background

Today, where antibiotic resistance is becoming more severe, more and more antibiotics have lost "shelter" from human health, which would have to severely threaten the health of an entire human. Lantibiotics, which are post-translationally modified polypeptides, have received considerable attention from scientists worldwide because of their novel chemical structure and a number of biological activities, as well as the virtually non-emergence of resistance. Bicereucin is used as a novel-structure bi-component lantibiotic, and the bi-component structure of Bicereucin contains 8D-configuration unnatural amino acids. Bicereucin is novel in chemical structure and shows strong antibacterial activity against many gram-positive pathogenic bacteria. However, bicereucin molecules, although having good antibacterial activity, also have strong mammalian erythrocyte hemolysis, which creates a great impediment for the future development of drug molecules.

Disclosure of Invention

The invention aims to solve the problem that Bicereucin molecules exert antibacterial activity on mammal erythrocytes by limiting the strong hemolysis of the Bicereucin molecules, and provides a Bicereucin mutant of a lantibiotic antibiotic, wherein the specific amino acid inside the Bicereucin molecules is subjected to site-directed mutagenesis by adopting an overlay PCR technology, so that a series of mutant molecules are expected to be obtained, the antibacterial activity of the Bicereucin molecules is reserved, and the hemolysis is obviously reduced.

In order to achieve the above purpose, the technical scheme provided by the invention is as follows: a variant of the lantibiotic antibiotic Bicereucin, which variant is a mutation of D-Ala at position 17 or 30 of Bsj alpha to L-Ala; the 19 th D-Abu or 31 st D-Ala of Bsjβ is mutated into any one of L-Ala, wherein the amino acid sequence of Bsjα is shown as SEQ ID No.3, and the amino acid sequence of Bsjβ is shown as SEQ ID No. 4.

The other technical scheme provided by the invention is as follows: a lantibiotic Bicereucin mutant gene is shown in any one of SEQ ID No.5, SEQ ID No.6, SEQ ID No.7 and SEQ ID No.8 as a coding sequence of a precursor peptide of the mutant.

The invention also provides application of the Bicereucin mutant of the lantibiotic, and the mutant is used for preparing the lantibiotic.

The invention also provides a lantibiotic comprising said mutant of Bsj alpha or Bsj beta.

Further, the antibiotic comprises a mutant in which D-Ala at position 17 or 30 of Bsjα is mutated to L-Ala, and Bsjβ.

Further, the antibiotic comprises a mutant in which D-Ala at position 17 or 30 of Bsjα is mutated to L-Ala, and a mutant in which D-Abu at position 19 of Bsjβ is mutated to L-Ala.

Further, the antibiotic comprises a mutant in which D-Ala at position 17 or 30 of Bsjα is mutated to L-Ala, and a mutant in which D-Ala at position 31 of Bsjβ is mutated to L-Ala.

Further, the antibiotic comprises a mutant in which D-Abu at position 19 of Bsjβ is mutated to L-Ala, and Bsjα.

Further, the antibiotic comprises a mutant in which D-Ala at position 31 of Bsj beta is mutated to L-Ala, and Bsj alpha.

The invention utilizes the overlay PCR technology to change the coding gene sequences of Bsj alpha and Bsj beta, constructs a required expression vector, enables the molecule to be artificially and randomly modified by the catalysis of in vivo post-modification enzyme, has the characteristics of simple and rapid operation, high yield of target products, environmental protection and the like; novel lantibiotic mutants of Bicereucin are provided, which mutants have significantly reduced hemolysis relative to the wild type; meanwhile, experiments prove that the biological functions of Bsj alpha, bsj beta and mutants thereof are proved, and the mutants of the Bsj alpha, bsj beta and mutants thereof have synergistic effect with the other wild type, so that the Bsj alpha, bsj beta and mutants have excellent antibacterial activity and low hemolytic property, and provide a material basis for preparing the lantibiotic antibiotics Bicereucin.

Drawings

FIG. 1 is a map of expression vector pETDuet-1;

FIG. 2 is a map of the expression vector pRSFDuet-1;

FIG. 3 is a diagram showing PCR results of structural genes and post-modification enzyme genes; wherein, (a) a map of PCR results for bsjA1, bsjA 2; (b) For bsjM, bsjJ _B Is a PCR result graph of (2);

FIG. 4 is a graph showing the results of purification of the precursor peptide BsjA1 and its mutants by RP-HPLC;

FIG. 5 is a diagram showing the results of high-resolution mass spectrum Q-TOF/MS detection of the precursor peptide BsjA1 and its mutants;

FIG. 6 is a graph showing the results of purification of the precursor peptide BsjA2 and its mutants by RP-HPLC;

FIG. 7 is a diagram showing the results of high-resolution mass spectrum Q-TOF/MS detection of the precursor peptide BsjA2 and its mutants;

FIG. 8 is a graph of the results of purification of Bsjα and its mutants by RP-HPLC, with the elution peaks for Bsjα and its mutants marked with asterisks);

FIG. 9 is a graph of the high resolution mass spectrum Q-TOF/MS detection results of Bsjα and its mutants;

FIG. 10 is a graph showing the results of purification of Bsj beta and its mutants by RP-HPLC, with the elution peaks of Bsj beta and its mutants marked with asterisks);

FIG. 11 is a diagram of the high resolution mass spectrum Q-TOF/MS detection results of Bsj beta and its mutants;

FIG. 12 is a graph showing the results of experiments on the antibacterial activity of Bsjα and Bsjβ and their mutants, 1, sterile ddH ₂ O；2,Bsjα+Bsjβ；3,Bsjα ^Ser17Ala +Bsjβ；4,Bsjα ^Ser30Ala +Bsjβ；5,Bsjα+Bsjβ ^Thr19Ala ；6,Bsjα+Bsjβ ^Ser31Ala ；

FIG. 13 is a graph showing the results of experiments on the hemolytic activities of Bsjα and Bsjβ and their mutants.

Detailed Description

In order that the invention may be readily understood, a more particular description thereof will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Biological materials such as experimental strains involved in the examples of the present invention are commercially available unless otherwise specified.

EXAMPLE 1 construction of Bicereucin molecular mutant expression vector and inducible expression

(1) Primer design and extraction of template genome

The downloaded genomic DNA sequence of the Bacillus cereus SJ strain is used for designing a primer (primer design software is Premier 5), and the designed primer is submitted to the biological engineering (Shanghai) limited company for synthesis. And extracting the genomic sequence of Bacillus cereus SJ strain (ARS, USA) as a template for PCR amplification; for the structural gene bsjA1 encoding the precursor peptide BsjA1 and the structural gene bsjA2 encoding the precursor peptide BsjA2, and the post-modification enzyme genes bsjM and bsjJ _B And carrying out PCR amplification to obtain the corresponding target gene fragment. The amplification primers are shown in Table 1.

TABLE 1 structural genes bsjA1 and bsjA2, and post-modifier genes bsjM and bsjJ _B Amplification primers of (2)

The culture medium of the wild strain Bacillus cereus SJ (ARS, USA) is LB liquid culture medium, and the nutrient component of the culture medium is 10g/L NaCl (national medicine, shanghai), 5g/L yeast powder (Oxoid, UK) and 10g/L peptone (Oxoid, UK). The culture temperature is 37 ℃, and the rotating speed of a shaking table (model of shaking table: shanghai spring MQD-B3R) is 220rpm/min. Measuring biomass of thallus with spectrophotometer (Nano-300, hangzhou Otsu), and measuring the biomass OD ₆₀₀ When=0.8, the cells were collected by centrifugation at 5000rpm/min for 10 minutes in a centrifuge (centrifuge model: eppendorf AG,5424HG 079802), and the supernatant was discarded. The genome of strain Bacillus cereus SJ1 was then extracted using a bacterial genome kit (cat# DP 302-02) from Beijing Tiangen, inc., see kit instructions for specific procedures. The concentration of the genome was measured with a micro-spectrophotometer (Nano-300, hangzhou Oreg.) and stored in a refrigerator at-20℃for further use.

(2) Amplification, recovery and purification of target gene fragment

A PCR amplification system (200. Mu.l) was prepared from PrimeSTAR Max Premix (cat# R045) produced by Takara Bio-engineering (Dalian) and the extracted genome, as well as primers and deionized water, and consisted of:

after preparation, the mixture was thoroughly mixed by pipetting with a micropipette (Eppendorf, germany) and 50. Mu.l of each PCR tube was dispensed, and amplification was started with a PCR amplification apparatus (Bio-Rad, USA). Structural genes bsjA1 and bsjA2 and post-modifier gene bsjJ _B The amplification procedure was as follows:

in addition, the post-modification enzyme gene bsjM amplification procedure was as follows:

after the PCR reaction procedure was completed, electrophoresis was performed with 1% (w/v) agarose gel (model of electrophoresis apparatus: beijing, junli JY300C type) for 30 minutes. The PCR electrophoresis result of the gene bsjA1 and bsjA2 is shown in FIG. 3 (a), and the post-modification enzyme gene bsjM and bsjJ _B The result of PCR electrophoresis of (a) is shown in FIG. 3 (b).

Then, the glue is cut by a glue cutting instrument (Beijing, tiangen Tgreen Transilluminator). The glue block is carried out by using a glue recovery kit (product number: #DP210-02) produced by Beijing Tiangen company, and the specific operation is shown in the specification of the kit. The recovered DNA fragment was subjected to concentration measurement by a micro spectrophotometer (Nano-300, hangzhou Otsu), and stored in a refrigerator at-20℃for use.

(3) Gibson assembly of DNA fragments

Prior to Gibson assembly, the expression vectors pETDuet-1 and pRSFDuet-1 (the maps of expression vectors pETDuet-1 and pRSFDuet-1 are shown in FIGS. 1 and 2, respectively) were first linearized with the DNA restriction endonuclease Nde I (NEB accession: #R0111S) at the site MCS2. The cleavage system (50. Mu.l) was as follows:

the enzyme digestion is carried out for 4 hours at 37 ℃, then the gel is cut and recovered, and the method is consistent with the recovery of DNA fragments amplified by PCR. The concentration of the recovered vector DNA fragment was measured by a micro spectrophotometer (Nano-300, hangzhou Otsu), and then stored in a refrigerator at-20℃for use. And (3) carrying out Gibson assembly on the obtained gene fragment and the linearized vector DNA to construct an expression vector. Expression vector pETDuet-BsjJ _B The Gibson assembly system (10 μl) is as follows:

incubate at 50℃for 40 min.

In addition, the Gibson assembly system (10. Mu.l) of the expression vector pRSFDuet-BsjM was as follows:

incubate at 50℃for 40 min.

(4) Heat shock transformation of E.coli DH 5. Alpha

The Gibson assembly solution was removed, E.coli DH 5. Alpha. Competent cells were thawed on ice for 3 min, and the Gibson assembly solution was gently added to the competent cells, gently mixed, and placed on ice for 30 min. Then placing the mixture in a constant temperature water bath kettle at 42 ℃ for heat shock for 1 minute, immediately inserting the mixture into ice and placing the mixture for 3 minutes. Mu.l of fresh sterile LB liquid medium without resistance was added and resuscitated on a constant temperature shaking table at 37℃for 1 hour. Centrifuging at 5000rpm for 2 min, discarding supernatant, blowing and suspending thallus with a pipetter, and collecting bsjJ _B Gene sampleThe solution is dripped on an LB solid flat plate containing ampicillin and is uniformly coated; samples of the bsjM gene were spread evenly by dripping onto LB solid plates containing kanamycin and then incubated in a 37 ℃ incubator for 6-12 hours.

(5) Identification of E.coli Positive transformants

Picking 6 transformants from the plate, inoculating into LB liquid medium containing corresponding antibiotics, shake culturing at 37deg.C for 8 hr, and waiting for bacterial liquid OD ₆₀₀ At a value of about 1.5, the cells were collected by centrifugation at 8000rpm for 2 minutes, and the supernatant was discarded. Plasmid was extracted using the plasmid miniprep kit (cat# D6942) manufactured by Omega company, and specific procedures are described in the kit instructions. The extracted plasmid fragments were measured for concentration by a micro-spectrophotometer (Nano-300, hangzhou Oreg.) and then sent to Qingdao Rui Biotechnology Co., ltd. For sequencing, and the correctly sequenced expression plasmid was stored in a refrigerator at-20℃for further use.

(6) Construction of expression vector pRSFDuet-6His-bsjA1/A2-BsjM

When the construction of the vector pRSFDuet-BsjM was completed, it was selected to linearize with the DNA restriction enzyme BamHI (NEB accession number: #R3136L) at the site MCS1. The cleavage system (50. Mu.l) was as follows:

and (3) enzyme cutting for 4 hours at 37 ℃, and then cutting glue for recovery, wherein the recovery method is as described above. The structural genes bsjA1 and bsjA2 were assembled with linearized vector prssfduet-BsjM to construct expression vectors. The Gibson assembly system (10. Mu.l) of the expression vector pRSFDuet-6His-bsjA1/A2-BsjM is as follows:

incubate at 50℃for 40 min. After the assembly, the heat shock transformation of E.coli DH 5. Alpha. Competent cells and the identification of positive transformants were performed as described above.

(7) The pRSFDuet-6His-bsjA1/A2-BsjM is used as a template, the corresponding sites of the structural genes bsjA1 and bsjA2 are subjected to site-directed mutagenesis by using the overlay PCR technology, and the gene sequences of the mutants are obtained as follows, wherein the underlined mutation sites:

mutant bsjA1 ^Ser17Ala The gene sequence of (2) is shown as SEQ ID No.5 in the sequence table:

ATGACAAATGAAGAAATTATTGTAGCATGGAAAAATCCAAAAGTAAGAGGTAAGAACATGCCATCTCACCCATCAGGAGTAGGATTCCAAGAATTATCAATTAATGAAATGGCGCAAGTAACAGGTGGAGCAGTTGAACAAAGAGCAACACCAGCAACACCAGCAACGCCTTGGCTTATTAAAGCAGCATATGTTGTATCAGGCGCAGGTGTTTCGTTTGTTGCAAGTTATATCACAGTTAATTAA。

mutant bsjA1 ^Ser30Ala The gene sequence of (2) is shown as SEQ ID No.6 in a sequence table:

ATGACAAATGAAGAAATTATTGTAGCATGGAAAAATCCAAAAGTAAGAGGTAAGAACATGCCATCTCACCCATCAGGAGTAGGATTCCAAGAATTATCAATTAATGAAATGGCGCAAGTAACAGGTGGAGCAGTTGAACAAAGAGCAACACCAGCAACACCAGCAACGCCTTGGCTTATTAAAGCATCATATGTTGTATCAGGCGCAGGTGTTTCGTTTGTTGCAGCATATATCACAGTTAATTAA。

mutant bsjA2 ^Thr19Ala The gene sequence of (2) is shown as SEQ ID No.7 in a sequence table:

ATGACAAATGAAGAAATCATTGTAGCATGGAAAAATCCAAAAGTAAGAGGTAAGAACATGCCATCTCACCCATCAGGAGTAGGATTCCAAGAATTATCAATTAATGAAATGGCGCAAGTAACAGGTGGAGCAGTTGAACAAAGAGCAACACCAACATTAGCAACACCATTAACTCCACATACACCGTATGCAGCATATGTTGTATCAGGTGGCGTAGTATCGGCAATTAGCGGTATTTTTTCAAACAATAAAACATGCCTAGGTTAA。

mutant bsjA2 ^Ser31Ala The gene sequence of (2) is shown as SEQ ID No.8 in the sequence table:

ATGACAAATGAAGAAATCATTGTAGCATGGAAAAATCCAAAAGTAAGAGGTAAGAACATGCCATCTCACCCATCAGGAGTAGGATTCCAAGAATTATCAATTAATGAAATGGCGCAAGTAACAGGTGGAGCAGTTGAACAAAGAGCAACACCAACATTAGCAACACCATTAACTCCACATACACCGTATGCAACATATGTTGTATCAGGTGGCGTAGTATCGGCAATTGCAGGTATTTTTTCAAACAATAAAACATGCCTAGGTTAA。

the gene fragments of the above mutants were synthesized using the corresponding primers in Table 2, and expression vectors of the respective mutant genes were obtained by referring to the construction methods of the expression vectors of the aforementioned structural genes bsjA1 and bsjA 2.

TABLE 2 amplification primers for each mutant of structural genes bsjA1 and bsjA2

(8) Heat shock transformation of E.coli BL21 (DE 3)

The expression vectors pRSFDuet-6His-bsjA1-BsjM and pRSFDuet-6His-bsjA2-BsjM were obtained _B Co-transformation into E.coli BL21 (DE 3) was performed as described above using colony PCR to identify positive transformants.

Taking the expression vector of each mutant of the structured genes bsjA1 and bsjA2 and pETDuet-BsjJ _B Co-transformation into E.coli BL21 (DE 3) was performed as described above using colony PCR to identify positive transformants.

Colony PCR procedures were consistent with the gene amplification procedures described previously. Meanwhile, a wild type E.coli BL21 (DE 3) monoclonal was used as a negative control.

(9) Inducible expression of a precursor peptide

A single clone of the positive transformant was inoculated into LB liquid medium containing ampicillin (100. Mu.g/ml) and kanamycin (50. Mu.g/ml), and cultured at 37℃for 8-12 hours at 200rpm in a shaker, to prepare a seed solution. Then, a large bottle of LB liquid medium was inoculated at a ratio of 1% (v/v), and cultured at 200rpm in a shaker at 37℃for about 3 hours. When the bacterial liquid OD ₆₀₀ When the value is 0.8, the bacterial liquid is taken out and cooled in ice water for 20 minutes, and the bacterial liquid is shaken once in the middle to be precooled uniformly. Then, IPTG (Ding Guo, beijing) was added to the super clean bench to a final concentration of 0.8mM to initiate induction. Placed in a shaker at 200rpm 18℃for 20 hours.

(10) Separation and purification of precursor peptides

After induction, the cells were collected by centrifugation at 6000rpm for 10 minutes using a refrigerated centrifuge (optionally, hunan), and the fermentation supernatant was discarded because the product was expressed intracellularly. Then, according to 1g wet cells 10ml of resuspended BufferA1 (20 mM NaH) was added ₂ PO ₄ 500mM NaCl,6M guanidine hydrochloride, 0.5mM imidazole, pH 7.5), the cells were resuspended, stirred with a glass rod and then crushed in a high-pressure homogenizer (ATS, canada) at 750bar for 15 minutes. The crushed solution was centrifuged at 14000rpm for 50 minutes with a refrigerated centrifuge (Thermo, USA), and the supernatant was filtered through a 0.45 μm filter membrane (forum, tianjin), and the filtrate was loaded into a 5ml nickel column (Boguy, shanghai) at a natural flow rate, and the loading was repeated three times. Washing 10-20 column volumes with hetero-protein Elution Buffer (BufferA1+30 mM imidazole, pH 7.5), and finally with Elutation Buffer (20 mM NaH) ₂ PO ₄ 500mM NaCl,4M guanidine hydrochloride, 1M imidazole, pH 7.5) completely eluted the sample, the elution volume was 2 times the volume of nickel material. The collected eluent is prepared to be separated and purified by a high performance liquid chromatographic column. After passing through a 0.45 μm filter membrane, the eluate was desalted and purified by a high performance liquid chromatograph (shimadzu, su zhou) with a C4 reverse phase column (feminomei, USA), and the liquid phase mobile phase a was: pure water plus 0.1% tfa; the mobile phase B is: 80% acetonitrile plus 0.1% TFA. The elution procedure was as follows:

after the target peak was collected, it was frozen with liquid nitrogen and then dried with a freeze-vacuum dryer (Yongzhuan, qingdao).

The results of purification of the precursor peptide BsjA1 and its mutants by RP-HPLC are shown in FIG. 4. The results of purification of the precursor peptide BsjA2 and its mutants by RP-HPLC are shown in FIG. 6.

(11) Mass spectrometric detection of precursor peptides

After obtaining the lyophilized precursor peptide, it was dissolved in deionized water and the molecular weight of the precursor peptide was checked for compliance with the theoretical molecular weight using a high resolution mass spectrometer Q-TOF/MS (Bruker, germany).

The results of detection of the precursor peptide BsjA1 and its mutants using high resolution mass spectrometry Q-TOF/MS are shown in FIG. 5. The results of detection of the precursor peptide BsjA2 and its mutants using high resolution mass spectrometry Q-TOF/MS are shown in FIG. 7.

(12) Excision of leader peptide

After the mass spectrum has detected that the molecular weight is correct, the lyophilized sample is dissolved in pure water, and then cleaved by the commercial endoprotease GluC (NEB, cat# P8100S) to remove the leader peptide and release the core peptide. The cleavage system (5 ml) was as follows:

GluC Reaction Buffer formula is: 50mM Tris-HCl;0.5mM Glu-Glu, pH8.0.

The cleavage system was placed in a 37℃incubator for 8 hours, and after the reaction was completed, 0.1% TFA was added to terminate the reaction.

The amino acid sequence of the precursor peptide BsjA1 is shown as SEQ ID No.1 in a sequence table:

MTNEEIIVAWKNPKVRGKNMPSHPSGVGFQELSINEMAQVTGGAVEQRATPATPATPWLIKASYVVSG AGVSFVASYITVNthe underlined part is the amino acid sequence of the core peptide Bsjα, as shown in SEQ ID No.3 in the sequence Listing, and the rest is the leader peptide.

The amino acid sequence of the precursor peptide BsjA2 is shown as SEQ ID No.2 in a sequence table:

MTNEEIIVAWKNPKVRGKNMPSHPSGVGFQELSINEMAQVTGGAVEQRATPTLATPLTPHTPYATYVV SGGVVSAISGIFSNNKTCLGthe underlined part is the amino acid sequence of the core peptide Bsj beta, as shown in SEQ ID No.4 in the sequence Listing, and the rest is the leader peptide.

The amino acid sequences of the precursor peptides of the mutants are respectively shown as SEQ ID No.9-12 in the sequence table.

The amino acid sequence of the core peptide of each mutant is the part from the QRA to the tail in the amino acid sequence shown in SEQ ID No.9-12 in the sequence table.

(13) Separation and purification of core peptides

After the cleavage reaction of the precursor peptide was completed, purification was performed by high performance liquid chromatography with a C18 reverse phase column (fenolme, USA), and the elution procedure was as follows:

the eluate of each peak was collected, frozen with liquid nitrogen, and dried with a vacuum freeze dryer.

The results of purification of Bsjα and its mutants by RP-HPLC are shown in FIG. 8. Bsj beta and its mutants were purified by RP-HPLC and the results are shown in FIG. 10.

(14) Mass spectrometric detection of core peptides

After drying, the components were dissolved in deionized water and the molecular weight of the core peptide was checked for compliance with the theoretical molecular weight using a high resolution mass spectrometer, Q-TOF/MS. The elution peak and elution time of the core peptide were recorded.

Bsjα and its mutants were detected by high resolution mass spectrometry Q-TOF/MS as shown in FIG. 9.

The results of detection of Bsj beta and its mutants by high resolution mass spectrometry Q-TOF/MS are shown in FIG. 11.

The invention uniformly replaces the codon of coding serine (Ser) or threonine (Thr) in the original gene with the codon (GCA) of coding L-alanine (L-Ala) by an amino acid site-directed mutagenesis technology, realizes the conversion from D-Ala or D-Abu generated after the serine (Ser) or threonine (Thr) is subjected to post-translational modification to L-Ala under the natural state, expects to obtain mutant molecules with reduced hemolytic activity and retained antibacterial activity, and provides theoretical guidance for the application of the molecules to clinical treatment in the future.

Example 2 functional verification of Bicereucin molecular mutant core peptide

(1) Antibacterial Activity experiments

Wild-type Bsj alpha, bsj beta and a series of mutant core peptides were dissolved in sterile deionized water and made into 100 μm stock for use. The Bacillus subtilis strain (ATCC, USA) was used as an indicator strain for the antibacterial activity test. First, the indicator bacteria were spread on a solid LB agar plate without resistance, and an incubator at 37 ℃Culturing for 10 hr, picking up single clone, inoculating into liquid LB culture medium, shake culturing at 37deg.C for about 4 hr, and culturing at OD ₆₀₀ When the ratio is equal to 0.4, the mixture is added into LB agar medium cooled to 45 ℃ according to the inoculation ratio of 2% (v/v), the mixture is evenly mixed, the plate is immediately poured, and the steam on the cover is dried in an ultra-clean workbench. Various combinations of the two core peptides and their mutants were then added dropwise to the plates and the change in antimicrobial activity was assessed by the sum of their inhibition zone sizes and MIC values.

As shown in FIG. 12 and Table 3, after the D-Ala at position 17 or 30 of Bsjα was mutated to L-Ala, the antibacterial activity of Bsjα was not greatly affected (MIC values of 1.5. Mu.M+0.75. Mu.M and 2.5. Mu.M+1.25. Mu.M, respectively, were added at a ratio of 2:1).

For Bsj.beta., the mutation from original D-Abu to L-Ala at position 19 or from original D-Ala to L-Ala at position 31 had little effect on the antibacterial activity of Bsj.beta. (MIC values were 2.0. Mu.M+1.0. Mu.M, added at a 2:1 ratio).

TABLE 3 Minimum Inhibitory Concentration (MIC) and inhibition zone size determination results

a, annotating: the size of the inhibition zone was tested on solid agar plates, the Minimum Inhibitory Concentration (MIC) was tested using a liquid growth inhibition assay, and the test strain was bacillus subtilis Bacillus subtilis strain 168.

(2) Rabbit erythrocyte hemolytic Activity experiment

Fresh rabbit erythrocytes were diluted to 5% (v/v) with PBS buffer, and the cells were collected by centrifugation at 4℃for 5 min with a refrigerated centrifuge 500g, and washed at least 5 times with PBS buffer until the supernatant became clear. Wild type Bsjα, bsjβ and their mutant core peptides were all dissolved in PBS buffer to prepare 150. Mu.M solutions. The core peptides were mixed with rabbit erythrocytes and then placed in 96-well plates and incubated with carbon dioxide in a carbon dioxide incubator at 37 ℃. mu.L of cultured cells were taken out every hour, diluted with 450. Mu.L of PBS buffer, and centrifuged at 500gCentrifuging at 4deg.C for 5 min to collect cells, collecting 200 μl supernatant, and measuring OD with enzyme-labeled instrument in 96-well plate ₄₁₅ Values, three replicates were run for each sample at the time of measurement.

As shown in FIG. 13, the hemolytic activity of all mutants was reduced, wherein the mutant showed the greatest effect on the hemolytic activity after the mutation of D-Ala at position 17 of Bsj alpha to L-Ala, and the hemolytic rate after the mutation was 16.5% -21.5% of that of the wild Bicereucin molecule at the same time.

The antibacterial activity experiment and the hemolytic activity experiment show that the Bsj alpha 17 th L-Ala mutant or the 30 th L-Ala mutant provided by the invention can be combined with wild Bsj beta, or Bsj beta 19 th L-Ala mutant or 31 st L-Ala mutant can be combined with wild Bsj alpha peptide, or Bsj alpha 17 th L-Ala mutant or 30 th L-Ala mutant can be combined with Bsj beta 19 th L-Ala mutant or 31 st L-Ala mutant at random to be used as excellent patent medicine molecules for preparing antibiotic medicines. Among them, the L-Ala mutant at position 17 of Bsjα is the best drug precursor in combination with wild-type Bsjβ.

Sequence listing

<110> university of Shandong

Shandong university Suzhou institute

<120> lantibiotic Bicerucin mutants and uses thereof

<141> 2022-05-17

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Gly Lys Asn Met Pro Ser His Pro Ser Gly Val Gly Phe Gln Glu Leu

20 25 30

Ser Ile Asn Glu Met Ala Gln Val Thr Gly Gly Ala Val Glu Gln Arg

35 40 45

Ala Thr Pro Ala Thr Pro Ala Thr Pro Trp Leu Ile Lys Ala Ser Tyr

50 55 60

Val Val Ser Gly Ala Gly Val Ser Phe Val Ala Ser Tyr Ile Thr Val

65 70 75 80

Asn

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Met Thr Asn Glu Glu Ile Ile Val Ala Trp Lys Asn Pro Lys Val Arg

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Gly Lys Asn Met Pro Ser His Pro Ser Gly Val Gly Phe Gln Glu Leu

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Ser Ile Asn Glu Met Ala Gln Val Thr Gly Gly Ala Val Glu Gln Arg

35 40 45

Ala Thr Pro Thr Leu Ala Thr Pro Leu Thr Pro His Thr Pro Tyr Ala

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Thr Tyr Val Val Ser Gly Gly Val Val Ser Ala Ile Ser Gly Ile Phe

65 70 75 80

Ser Asn Asn Lys Thr Cys Leu Gly

85

<210> 3

<211> 35

<212> PRT

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Gln Arg Ala Thr Pro Ala Thr Pro Ala Thr Pro Trp Leu Ile Lys Ala

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Ser Tyr Val Val Ser Gly Ala Gly Val Ser Phe Val Ala Ser Tyr Ile

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<400> 4

Gln Arg Ala Thr Pro Thr Leu Ala Thr Pro Leu Thr Pro His Thr Pro

1 5 10 15

Tyr Ala Thr Tyr Val Val Ser Gly Gly Val Val Ser Ala Ile Ser Gly

20 25 30

Ile Phe Ser Asn Asn Lys Thr Cys Leu Gly

35 40

<210> 5

<211> 246

<212> DNA

<213> Artificial Sequence

<400> 5

atgacaaatg aagaaattat tgtagcatgg aaaaatccaa aagtaagagg taagaacatg 60

ccatctcacc catcaggagt aggattccaa gaattatcaa ttaatgaaat ggcgcaagta 120

acaggtggag cagttgaaca aagagcaaca ccagcaacac cagcaacgcc ttggcttatt 180

aaagcagcat atgttgtatc aggcgcaggt gtttcgtttg ttgcaagtta tatcacagtt 240

aattaa 246

<210> 6

<211> 246

<212> DNA

<213> Artificial Sequence

<400> 6

atgacaaatg aagaaattat tgtagcatgg aaaaatccaa aagtaagagg taagaacatg 60

ccatctcacc catcaggagt aggattccaa gaattatcaa ttaatgaaat ggcgcaagta 120

acaggtggag cagttgaaca aagagcaaca ccagcaacac cagcaacgcc ttggcttatt 180

aaagcatcat atgttgtatc aggcgcaggt gtttcgtttg ttgcagcata tatcacagtt 240

aattaa 246

<210> 7

<211> 267

<212> DNA

<213> Artificial Sequence

<400> 7

atgacaaatg aagaaatcat tgtagcatgg aaaaatccaa aagtaagagg taagaacatg 60

ccatctcacc catcaggagt aggattccaa gaattatcaa ttaatgaaat ggcgcaagta 120

acaggtggag cagttgaaca aagagcaaca ccaacattag caacaccatt aactccacat 180

acaccgtatg cagcatatgt tgtatcaggt ggcgtagtat cggcaattag cggtattttt 240

tcaaacaata aaacatgcct aggttaa 267

<210> 8

<211> 267

<212> DNA

<213> Artificial Sequence

<400> 8

atgacaaatg aagaaatcat tgtagcatgg aaaaatccaa aagtaagagg taagaacatg 60

ccatctcacc catcaggagt aggattccaa gaattatcaa ttaatgaaat ggcgcaagta 120

acaggtggag cagttgaaca aagagcaaca ccaacattag caacaccatt aactccacat 180

acaccgtatg caacatatgt tgtatcaggt ggcgtagtat cggcaattgc aggtattttt 240

tcaaacaata aaacatgcct aggttaa 267

<210> 9

<211> 81

<212> PRT

<213> Artificial Sequence

<400> 9

Met Thr Asn Glu Glu Ile Ile Val Ala Trp Lys Asn Pro Lys Val Arg

1 5 10 15

Gly Lys Asn Met Pro Ser His Pro Ser Gly Val Gly Phe Gln Glu Leu

20 25 30

Ser Ile Asn Glu Met Ala Gln Val Thr Gly Gly Ala Val Glu Gln Arg

35 40 45

Ala Thr Pro Ala Thr Pro Ala Thr Pro Trp Leu Ile Lys Ala Ala Tyr

50 55 60

Val Val Ser Gly Ala Gly Val Ser Phe Val Ala Ser Tyr Ile Thr Val

65 70 75 80

Asn

<210> 10

<211> 81

<212> PRT

<213> Artificial Sequence

<400> 10

Met Thr Asn Glu Glu Ile Ile Val Ala Trp Lys Asn Pro Lys Val Arg

1 5 10 15

Gly Lys Asn Met Pro Ser His Pro Ser Gly Val Gly Phe Gln Glu Leu

20 25 30

Ser Ile Asn Glu Met Ala Gln Val Thr Gly Gly Ala Val Glu Gln Arg

35 40 45

Ala Thr Pro Ala Thr Pro Ala Thr Pro Trp Leu Ile Lys Ala Ser Tyr

50 55 60

Val Val Ser Gly Ala Gly Val Ser Phe Val Ala Ala Tyr Ile Thr Val

65 70 75 80

Asn

<210> 11

<211> 88

<212> PRT

<213> Artificial Sequence

<400> 11

Met Thr Asn Glu Glu Ile Ile Val Ala Trp Lys Asn Pro Lys Val Arg

1 5 10 15

Gly Lys Asn Met Pro Ser His Pro Ser Gly Val Gly Phe Gln Glu Leu

20 25 30

Ser Ile Asn Glu Met Ala Gln Val Thr Gly Gly Ala Val Glu Gln Arg

35 40 45

Ala Thr Pro Thr Leu Ala Thr Pro Leu Thr Pro His Thr Pro Tyr Ala

50 55 60

Ala Tyr Val Val Ser Gly Gly Val Val Ser Ala Ile Ser Gly Ile Phe

65 70 75 80

Ser Asn Asn Lys Thr Cys Leu Gly

85

<210> 12

<211> 88

<212> PRT

<213> Artificial Sequence

<400> 12

Met Thr Asn Glu Glu Ile Ile Val Ala Trp Lys Asn Pro Lys Val Arg

1 5 10 15

Gly Lys Asn Met Pro Ser His Pro Ser Gly Val Gly Phe Gln Glu Leu

20 25 30

Ser Ile Asn Glu Met Ala Gln Val Thr Gly Gly Ala Val Glu Gln Arg

35 40 45

Ala Thr Pro Thr Leu Ala Thr Pro Leu Thr Pro His Thr Pro Tyr Ala

50 55 60

Thr Tyr Val Val Ser Gly Gly Val Val Ser Ala Ile Ala Gly Ile Phe

65 70 75 80

Ser Asn Asn Lys Thr Cys Leu Gly

85

Claims

1. A variant of the lantibiotic antibiotic Bicereucin, characterized in that: the mutant is that D-Ala at 17 th or 30 th position of Bsj alpha is mutated into L-Ala; the 19 th D-Abu or 31 st D-Ala of Bsjβ is mutated into any one of L-Ala, wherein the amino acid sequence of Bsjα is shown as SEQ ID No.3, and the amino acid sequence of Bsjβ is shown as SEQ ID No. 4.

2. A lantibiotic mutant gene of Bicereucin, characterized in that: the gene is the coding sequence of the precursor peptide of the mutant as shown in any one of SEQ ID No.5, SEQ ID No.6, SEQ ID No.7 and SEQ ID No. 8.

3. Use of a variant of the lantibiotic according to claim 1, characterised in that: the mutant is used for preparing the lantibiotic.

4. A lantibiotic, characterized in that: the antibiotic comprising the mutant of claim 1.

5. The lantibiotic according to claim 4, characterised in that: the antibiotics comprise mutants of Bsjα in which D-Ala at position 17 or 30 is mutated to L-Ala, and Bsjβ.

6. The lantibiotic according to claim 4, characterised in that: the antibiotics include mutants in which D-Ala at position 17 or 30 of Bsjα is mutated to L-Ala, and mutants in which D-Abu at position 19 of Bsjβ is mutated to L-Ala.

7. The lantibiotic according to claim 4, characterised in that: the antibiotics include mutants in which D-Ala at position 17 or 30 of Bsjα is mutated to L-Ala, and mutants in which D-Ala at position 31 of Bsjβ is mutated to L-Ala.

8. The lantibiotic according to claim 4, characterised in that: the antibiotics comprise mutants of Bsjβ with the D-Abu mutation at position 19 to L-Ala, and Bsjα.

9. The lantibiotic according to claim 4, characterised in that: the antibiotics comprise mutants of Bsjβ with D-Ala at position 31 mutated to L-Ala, and Bsjα.