CN1208345C - Trimutant of recombinant human interleukin-2 and its preparation method - Google Patents

Abstract

The present invention relates to a trimutant of recombinant human interleukin-2, and a preparation method, which has the purpose that the human interleukin-2 (hIL-2) is reformed by a genetic engineering method. The activity of three-position point mutation interleukin-2 is prepared and is proved to be 4.3 times higher than that of natural human interleukin, a pPIC9K-IL-2-3m plasmid is constructed by obtaining three-position point mutation interleukin-2cDNA, KM 71 Pasteu-Pichia yeast is converted, and three-position point mutation interleukin-2 protein is obtained from supernatant fluid fermented by pPIC9K-IL-2-3m KM71 yeast, namely that the 18 position amino acid, the 19 position amino acid and the 125 position amino acid of natural interleukin-2 are respectively changed into methionine, serine and lactamine.

Description

Recombinant human interleukin--2's Trimutant and preparation method

Technical field:

The present invention relates to recombinant human interleukin--2's mutant and preparation method

Background technology:

Human Inter Leukin-2 (hIL-2) has three cysteine residues, wherein 58 and 105 s' halfcystine forms intramolecular disulfide bond, and 125 sulfydryl is free, and the method by rite-directed mutagenesis replaces 125 halfcystine with Serine or L-Ala, its active rising.The substituent activity of halfcystine of 125 of aminoacid replacement with other is nearly all constant.Though the biological activity of the substituent of 58 or 105 halfcystines descends, however the mutant of 58 halfcystine substituents compare with the mutant of 105 halfcystine substituents, vigor descends more than 20 times.Might play an important role by 58 halfcystines aminoacid sequence on every side.By contrast, near the amino acid importance 105 is very different in the structure function of hIL-2.On the other hand, why to lose activity may be owing to form the intramolecular disulfide bond of mispairing between 105 and 125 halfcystines to the mutant of 58 halfcystine substituents.In order to estimate the correct importance of disulfide linkage, replace three and two mutain of halfcystine respectively with the synthetic L-Ala in polymerase chain reaction, be named A58/105/125 and A58/125, on the CTLL-2 cell, mix analysis and show with the thymidine method.Have only 0.5-2% though these two mutant are compared with the vigor of wild-type hIL-2, they many 50-200 doubly than the vigor of A58, and A58 is exactly the mutant that replaces halfcystine with L-Ala at 58.Receptor competition shows that in conjunction with experiment mutant A58/125 and A58/105/125 are for the IL-2 acceptor of high-affinity than the high 5-25 of A58 doubly.These results show that mutant A58 vigor sharply descends, may be because 105 and 125 halfcystines form wrong disulfide linkage (Rang Y, Lee N, Liang S.M.Analysis of IL-2 functional structure by multiplecysteine substitutions.Biochem.Biophys.Res.1992;

The 125Cys point mutation is the Ala that Ala or Ser obtain among the hIL-2 ¹²⁵IL-2 and Ser ¹²⁵IL-2 does not have can form dimer, specific activity height, Heat stability is good, advantages such as the interior transformation period prolongation of body.At present, two kinds of novel I L-2 are now by pilot scale, enter clinical experimental stage (Tang Jianwei, Liu Aiping, Yu Jianliang. the thermally-stabilised superiority of two kinds of novel interleukin IIs. biotechnology journal 1996,12 (4), 448-454.).In addition, adjacent two the site mutation bodies of hIL-2 (L18M/L19S) have another name called 2D ₁,, all identical with wild-type hIL-2 in structural integrity with aspect high-affinity IL-2 receptor binding capacity two.After general hIL-2/IL-2 receptor complex enters corpusculum in the acid born of the same parents (acidic endosomalcompartment) by receptor-mediated endocytosis internalization, wild-type hIL-2 is often entered in the lysosome by sorting together with IL-2R β γ and degrades, and the α subunit that discharges turns back to cell surface and reenters recirculation (Fallon E.M, Liparoto S.F, Lee K.J et al.Increasedendosomal sorting of ligand to recycling enhances potency of an interleukin-2 analog.J.Biol.Chem.2000; 275 (10): 6790-6797.).But 2D ₁Enter in the acid born of the same parents behind the corpusculum by the receptor-mediated internalization of high-affinity hIL-2, in the born of the same parents that bring by mutain in the corpusculum subtle change of pH value disturbed ligand-receptor interaction, IL-2 and the sorting transportation change of IL-2 receptor complex in born of the same parents cause making a variation, some is not sorted in the lysosome degraded and remains among the 2D1 of internalization, and is entered recirculation again by sorting.The 2D1 transformation period that shows after measured is longer 36 hours than wild-type hIL-2, therefore the short cell fission proliferation function of 2D1 variant protein obtains very big enhancing, biologic activity improves (Hemar A more than 2 times, Subtil A, Lieb, M.J et al.Endocytosis ofinterleukin-2 receptors in human T lymphocytes:distinct intracellular localizationand fate of the receptor alpha, beta and gamma chains.J.Cell.Biol.1995; 129 (1): 55-64.).

For a long time, people with intestinal bacteria as host expresses multiple protein, comprising IL-2.But itself also exists some defectives this system: 1. as a kind of prokaryotic expression system, lack and modify behind the Eukaryotic protein translation and processing, as shear, glycosylation, form disulfide linkage etc.; 2. expressed proteins is many exists with the inclusion body form, needs could recover conformation and activity through complicated renaturation; 3. background albumen is a lot, the purifying trouble; 4. expression amount generally is not very high.Since 1997, developed the yeast cell to express system.What use at first is yeast saccharomyces cerevisiae, and also is used to express IL-2, but also there is its limitation in this system, is not desirable host.As lack strong promotor, and secernment efficiency is poor, and expression strain is stable inadequately, and expression plasmid is easy to lose etc.In view of this, people have been developed yeast expression system of new generation-Pichia Pastoris pichia pastoris phaff system, i.e. methanol yeast expression system.As eukaryotic expression system, methanol yeast has the not available advantage of many other protein expression systems: 1. have distinctive strong alcohol oxidase gene (AOXI) promotor, with methyl alcohol can strict regulation and control foreign protein expression; 2. as eukaryotic expression system, processing after expressed proteins can be translated and modification (as glycosylation), thus make the albumen biologically active that gives expression to, 3. complete fermentation process is arranged, can the high-density cultured continuously, dry cell weight even can reach more than the 120g/L in fermentor tank; 4. nutritional requirement is low, and growth is fast, can grow in the non-selective substratum of cheapness, and additional salt, VITAMIN get final product, and are convenient to suitability for industrialized production; 5. expression amount height, many albumen can reach every liter of above level of gram; 6. expressed proteins both can be present in the born of the same parents in Pichia Pastoris, can secrete to born of the same parents again.Excretory target protein matter accounts for all by more than 30% of secretory protein, and Pichia self excretory albumen (background albumen) is considerably less, very helps purifying; 7. degree of glycosylation is low.Therefore, this is a kind of FA expression system.In view of this, utilizing the secretor type pichia pastoris phaff to express IL-2, is very effective.

Summary of the invention:

Because the mispairing of IL-2 disulfide linkage in actual purifying, the IL-2 of purifying is stable inadequately, and whole productive rate is very low, so the present invention overcomes these shortcomings by the structure that changes IL-2 with replacing expression vector and system.

The object of the present invention is to provide a kind of recombinant human interleukin--2's three site mutation body and preparation methods, improve Human Inter Leukin-2's output and activity.

In order to realize the foregoing invention purpose, technical scheme of the present invention is: change 18 leucines of the natural IL-2 of people into methionine(Met), 19 leucines change Serine into, 125 halfcystines change L-Ala into, obtain one three site mutation recombinant human interleukin--2, as shown in Figures 2 and 3, the english abbreviation of leucine, methionine(Met), Serine, halfcystine, L-Ala is respectively Leu, Met, Ser, Cys and Ala.Three site mutation recombinant human interleukin--2 its preparation methods are:

Design 4 nucleotide primers:

(1) primer 1,5 ' GCG AAGTCAGTGTTGAGATGATGCTTTGCGCAAAGG3 '

(2) primer 2,3 ' CTGTAAATCAGACAATTAAATG5 '

(3) primer 3,5 ' GCACGT AGCACCTACTTCAAGTTCTAC3 '

(4) primer 4,5 ' GCATTTA

TCTGATTTACAG3 '

Wherein primer 1 and primer 4 are one group, and primer 2 and primer 3 are one group, are that template is carried out PCR with natural human interleukin II cDNA, and preceding two groups PCR product is merged, and the PCR product that is combined with primer 1 and primer 3 carries out PCR the 3rd time.Contain EcoR I restriction enzyme site in the primer 1, termination codon, 125 Cys change a complementary sequence of Ala and ripe human IL-2's 3 ' terminal portions amino acid encoding gene into, primer 2, primer 3 contains SnaB I restriction enzyme site, initiation codon and ripe human IL-2's 5 ' terminal portions amino acid coding, primer 4 is a mutant primer, wherein 18,19 leucines are mutated into 18 Met and 19 Ser respectively.Through behind 3 PCR, obtain three site mutation Human Inter Leukin-2s' dna fragmentation, the low melting-point agarose electrophoresis reclaims the 0.4kb band.The PCR product that finally obtains is the IL-2DNA fragment that contains SnaBI and EcoR I restriction enzyme site and 18,19 and 125 sudden changes, reclaims, and cuts enzyme with SnaB I and EcoRI enzyme and cuts, reclaim, be cloned into then in the pPIC9K eukaryon expression plasmid, transform TOP10F ' bacterial strain, identify the back amplification.Obtain pPIC9K- ¹⁸Met- ¹⁹Ser- ¹²⁵Ala-rhIL-2 plasmid, sequencing result are as shown in Figure 2.Prove that 18 CTG have changed ATG into, 19 CTG have changed TCT into, and 125 TGT have changed GCG into, are the three site mutation Human Inter Leukin-2s that we need.Then with pPIC9K- ¹⁸Met- ¹⁹Ser- ¹²⁵The Ala-rhIL-2 plasmid transforms the KM71 pichia pastoris phaff, and obtaining host cell is pichia pastoris phaff KM71/pPIC9K- ¹⁸Met- ¹⁹Ser- ¹²⁵Ala-rhIL-2 by this host cell of inducing culture, obtains three site mutation Human Inter Leukin-2 albumen from its fermented supernatant fluid, prove our mutain by WESTERN BLOT detection expression product engram analysis and the order-checking of N end.By selecting storng-acid cation exchange resin and gel column purifies and separates three site mutation recombinant human interleukin--2s for use, can obtain the purpose product of 95% above purity.With the CTLL-2 cell three site mutation recombinant human interleukin--2s are surveyed work, its specific activity standard substance are high 4.3 times.

IL-2 by structural modification and replacing expression vector and system has following advantage at least:

The first, the activity of raising interleukin II is higher about 4.3 times than standard substance.

The second, the stability of raising interleukin II.Because 125 halfcystines are free in the wild-type interleukin II molecule, be easy to disulfide linkage or intermolecular disulfide formation that halfcystine with 58 or 105 forms mispairing and cause dimeric formation, be unfavorable for the stable of interleukin II, then there is not the problem of disulfide linkage mispairing in 125 alanine type interleukin IIs.In addition, because yeast to the glycosylation modified effect that interleukin II carries out, makes interleukin II be difficult for aggregate and precipitate.

The 3rd, be easy to purifying, in the purge process of reconstituted inter leukin-2, interleukin II will be reduced agent and be reduced to primary structure, and then be oxidized to activated interleukin II, because 125 halfcystines are free, be easy to the disulfide linkage that halfcystine with 58 or 105 forms mispairing and cause the formation of isomer or intermolecular disulfide formation to cause dimeric formation, the isomer of these formation and dimer on the one hand to purifying make troubles/specific activity is low on the other hand.Then there is not the problem of disulfide linkage mispairing in 125 halfcystines by the interleukin II that L-Ala replaces, thereby help the purifying of interleukin II.In addition, by secretion type Pichi expression system expression-secretion interleukin II, background albumen is considerably less, is easy to very much purifying.

The 4th, translation post-treatment modification ability is strong.Yeast expression system is an eukaryotic expression system, can carry out expression product glycosylation modified, thereby obtain more product near Ziren body endogenous IL-2.

By special design of the present invention, demonstrate fully the high efficiency of high reactivity and expression vector and/or the engineering bacteria of IL-2 of the present invention.

Description of drawings:

Fig. 1 is pPIC9K- ¹⁸Met- ¹⁹Ser- ¹²⁵The structure synoptic diagram of Ala-rhIL-2 plasmid;

Fig. 2 is that the sequence of natural hIL-2 and three site mutation rhIL-2 genes compares;

Fig. 3 is the comparison of human IL-2's aminoacid sequence and three site mutation rhIL-2 aminoacid sequences;

Fig. 4 is three site mutation rhIL-2 expression product engram analysis figure;

Fig. 5 is that mtt assay is measured the active figure of three site mutation rhIL-2;

Fig. 6 is the direct graphing method of three site mutation rhIL-2 activity units.

Embodiment:

Example I

One, the structure of the clone of three site mutation hIL-2 genes, amplification and pPIC9K plasmid

We design and are synthetic automatically at dna synthesizer with the tris phosphite method, obtain four primers, primer 1,5 ' GCG through the urea-denatured glue purification of 20% acrylamide 7mol/L AAGTCAGTGTTGAGATGATGCTTTG

AAAGG3 ', primer 2,3 ' CTGTAAATCAGACAATTAAATG5 ', primer 3,5 ' GCACGT

AGCACCTACTTCAAGTTCTAC3 ', primer 4,5 ' GCATTTA TCTGATTTACAG 3 '.Contain EcoR I restriction enzyme site in the primer 1, termination codon, ¹²⁵One complementary sequence of Ala and ripe human IL-2's 3 ' terminal portions amino acid encoding gene, totally 43 bases, primer 2, totally 22 bases, primer 3 contains SnaB I restriction enzyme site, initiation codon and ripe hIL-2 5 ' terminal portions amino acid coding, totally 33 bases, primer 4 is a mutant primer, and wherein 18,19 leucines are mutated into ¹⁸Met, ¹⁹Ser, totally 22 bases.Do pcr amplification from the hIL-2 full length cDNA sequence with above-mentioned four primers, amplification PCR products is except that containing the mutator gene zone, and two ends also have restriction endonuclease sites SnaB I and EcoR I.Pcr amplification reaction, template: human IL-2 cDNA, 94 ℃ of sex change 5 ', then 94 ℃ 45 seconds 60 ℃ 45 seconds 72 ℃ 1 minute, 25 cyclic amplification products present the dense area band of 0.4Kb size in agarose electrophoresis, conform to the result of design.The segmental product of the 0.4Kb of amplification is cut three site mutation IL-2 with SnaB I enzyme earlier and is inserted son ⁸Met- ¹⁹Ser- ¹²⁵Ala-rhIL-2 and pPIC9K empty carrier.Press table 1 program

Table 1 SnaB I enzyme is cut DNA and carrier

Content property management 3 adds volume pipe 4 and adds volume

Three site mutation rhIL-2,20 μ L, about 5 μ g pPIC9K empty carriers, 10 μ L, 25 μ g

Insert son

SnaB?I 1.5μL 1.5μL

buffer 4μL 4μL

Redistilled water 14.5 μ L 24.5 μ L

Cumulative volume 40 μ L 40 μ L

Cut IL-2 with SnaB I enzyme and insert son and pPIC9K empty carrier.Pipe 3 and pipe 4 are cut 2h at 37 ℃ of enzymes respectively in the table 1.Use Silver Beads DNA glue to reclaim test kit, from reaction system, remove restriction enzyme, reclaim and concentration of DNA.Its concrete operations are as follows: the pipe 3 at cumulative volume 50 μ L adds 10 μ L distilled waters respectively successively with managing in 4, add 3 times of volume lysates from reclaiming test kit, the centrifugal supernatant liquor that removes, add 10 μ L granulated glass sphere suspensions, be adsorbed onto DNA on the granulated glass sphere with the elutriant wash-out respectively at last, with the distilled water constant volume to 34.5 μ L.Then cut with EcoR I enzyme.In 34.5 μ L volumes of pipe 3 that contains three site mutation IL-2 insertion and the pipe 4 that contains pPIC9K, add buffered soln 4.0 μ L respectively successively, EcoR I 1.5 μ L add 20 μ L granulated glass sphere suspensions, centrifugal abandoning supernatant, with elutriant wash-out granulated glass sphere, use the distilled water constant volume to 15 μ L.From manage 3 and pipe respectively get 5 μ L 4, the sepharose with 1% carries out electrophoresis.Check that carrier and three site mutation IL-2 insert the amount of son, general three site mutation IL-2 insert son: carrier=3: 1.Last restriction enzyme flush end connects.In the Ep pipe, add three site mutation IL-2 successively and insert sub 10 μ L, use the dephosphorylized plasmid vector 1 μ L of test kit, T ₄Dna ligase, 1 μ L, 50% Macrogol 4000 damping fluid, 2 μ L, the connection damping fluid 2 μ L of concentrated 10 times of volumes, distilled water 4 μ L, final volume is 20 μ L.Incubate bath at 14～16 ℃ and spend the night 1.5% low melting-point agarose gel electrophoresis.Behind the electrophoresis, reclaim test kit with Silver Beads DNA glue and reclaim recon.Obtain pPIC9K- ¹⁸Met- ¹⁹Ser- ¹²⁵The Ala-rhIL-2 plasmid, its building process as shown in Figure 1.This plasmid is with CaCL then ₂Method transformed into escherichia coli Top10F ', pPIC9K-is extracted in amplification in a large number ¹⁸Met- ¹⁹Ser- ¹²⁵The Ala-rhIL-2 recon.It is carried out dna sequence analysis.Adopt the terminal cessation method of two deoxidations of Sanger and the M13 of Messing to clone a sequencing system, use TaqDNA polysaccharase catalyzed reaction, and carry out the PAGE automatic sequencing by fluorescent mark, its sequence is seen Fig. 2.

Two, pPIC9K- ¹⁸Met- ¹⁹Ser- ¹²⁵The Ala-rhIL-2 plasmid transforms the pPIC9K-that Pichia Pastoris bacterial strain KM711. gets enough pure about 8 μ g ¹⁸Met- ¹⁹Ser- ¹²⁵The empty pPIC9K plasmid of the about 1ng/ μ of Ala-rhIL-2 and concentration L after Sal I linearization for enzyme restriction, is made low-melting Agrose glue with magnificent Shun's test kit and is reclaimed, for conversion is got ready.2. the complete red strain cell of picking KM71 is inoculated among the 10mL YPD, and 28～30 ℃ of 250～300rpm shake training and spend the night.3. the KM71 yeast cell liquid of dilution 10mL YPD incubated overnight is to OD ₆₀₀=0.1～0.2.28～30 ℃ are shaken training and allow the growth of KM71 cell up to OD ₆₀₀Reach 0.6～1.0, this process approximately needs 4～6hr.

4. the centrifugal 5min precipitate K of 500xg room temperature M71 cell, abandoning supernatant.

5. the KM71 cell precipitation is suspended among the 10mL damping fluid I, does not require cultivation.

6.500xg the centrifugal 5min precipitate K of room temperature M71 cell, abandoning supernatant.

7.KM71 cell precipitation is suspended among the 1mL damping fluid I, this moment, competence KM71 cell preparation was good.

8. KM71 competent cell 50 μ L are forwarded to the 1.5mL sterilization that installed to label in 200 minutes and have in the centrifuge tube of screw cap.

9. add the linearizing pPIC9K-of the about 4 μ g of 5 μ L ¹⁸Met- ¹⁹Ser- ¹²⁵Ala-rhIL-2 is in 50 μ L competence KM71 cells.

10. add the 1mL solution II to pPIC9K- ¹⁸Met- ¹⁹Ser- ¹²⁵In the Ala-rhIL-2/KM71 cell mixture, wortex device or finger play the test tube mixing.

11. 30 ℃ of heat insulating culture conversion reactions are 1 hour in ice bath or incubator.Per 15 minutes vortexs or springing test tube mixing conversion reaction.In order to avoid transformation efficiency reduces.

12. 42 ℃ of heat-shockeds are 10 minutes in 42 ℃ of heating installations or water-bath.

13. the centrifugal 10min precipitation of 3000xg room temperature pPIC9K- ¹⁸Met- ¹⁹Ser- ¹²⁵The Ala-rhIL-2/KM71 cell, abandoning supernatant.

14. suspension pPIC9K- ¹⁸Met- ¹⁹Ser- ¹²⁵The Ala-rhIL-2/KM71 cell is in the 1mL solution III.

15. the centrifugal 10min of 3000xg room temperature, sedimentation cell, abandoning supernatant.

16. suspension pPIC9K- ¹⁸Met- ¹⁹Ser- ¹²⁵The Ala-rhIL-2/KM71 cell is deposited in 100～150 μ L solution III.

17. whole conversion fluid is coated on the RDB, was cultivated 2～4 days for 30 ℃.

18. totally 6 of two covers, 96 orifice plates, three in a cover.With the rifle head of sterilization, in each micropore, add 200 μ LYPD.

19. with sterilization toothpick single His of inoculation in each hole of first cover, 96 orifice plates ⁺Transformant also stirs with suspension cell.

20. cover 96 orifice plate lids, cultivated 2 days, and needn't vibrate for 30 ℃.

21. after 2 days, get 96 new orifice plates and in each hole, add 190 μ LYPD.

Be inoculated into the second cover microwell plate 22. from first cover, 96 orifice plates, get 10 μ L with multichannel pipettor.Guarantee that second cover, 96 orifice plates carry out mark and arrange so that route that can retaining hole by certain way.

23. close the lid and at 30 ℃ of incubated overnight second cage plates.

24. second day, repeated for the 5th, 6 steps, obtain the 3rd cover microwell plate.Note clone's continuous growth and get liquid and can make their all clones reach identical cell density.

25. after cultivating, get the 3rd cover 96 orifice plates and blow and beat each hole suspension cell with rifle up and down at 100 μ L capacity places with the multiple tracks rifle.

26. to the YPD plate, the YPD plate contains the G418 final concentration and is respectively 0,0.25 from each hole mid point 10 μ L, and 0.50,0.75,1.00,1.50,1.75,2.00,3.00 and 4.00mg/mL.Stamp grid with the multiple tracks rifle by the fixed mode point sample or under flat board.

27. allow liquid infiltrate, 30 ℃ of culture plates then, 2,3, check anti-G418 clone after 4 or 5 days, obtain the clone of high copy, promptly contain the pichia pastoris phaff host cell-pichia pastoris phaff KM71/pPIC9K-of three site mutation recombinant human interleukin--2 genes ¹⁸Met- ¹⁹Ser- ¹²⁵Ala-rhIL-2.

Three, three expression of site mutation rhIL-2 in methanol yeast KM71

The expression of foreign protein in methanol yeast in two steps, i.e. thalli growth and protein induced expression.Earlier on the substratum that with glycerine is carbon source, cultivate thalline, reach certain OD value after, centrifugal, abandoning supernatant, it is abduction delivering in the substratum of carbon source that thalline is suspended in methyl alcohol, adds methyl alcohol one time every 24 hours, to remedy the loss of methyl alcohol.The condition of optimization expression at first is as composition of aeration status, pH value, substratum etc.In case top condition is determined, then can amplify in proportion, goes to large scale fermentation from shake-flask culture.

1. will filter out His ⁺Mut ^sMono-clonal is inoculated in 2mL YPD test tube, and 30 ℃ of 300rpm overnight incubation are inoculated 500 triangular flasks of going into to contain 100mL BMGY with 1%.

30 ℃ of 300rpm cultivated about 16～18 hours, to OD ₆₀₀=3～6.

2. the centrifugal 5min of 1500～3000xg collects somatic cells under the room temperature.Abduction delivering, abandoning supernatant also is suspended in the BMMY substratum the original initial nutrient solution volume with 1/5 to 1/10, promptly about 10～20mL with somatic cells precipitation.

3. thallus suspension liquid is placed the 100mL triangular flask, cover triangular flask, put back to the incubator continued growth again with the gauze or the scrim of 2 layers of sterilization.

4. per 24 hours add 100% methyl alcohol to final concentration is 0.5%, keeps inducing.

5. each following time all will be shifted 1mL and be expressed liquid in the 1.5mL centrifuge tube, and time point is: 0,24 hour, and 48 hours, 72 hours, 96 hours, 120 hours and 144 hours.These samples will be used for analyzing expression level and determine to induce the only time of back to gather in the crops supernatant liquor.Use desk centrifuge with maximum velocity centrifugation 2～3min under the room temperature.

6. shift supernatant liquor in different pipes, store supernatant liquor and cell precipitation for-80 ℃ and analyze until preparing.Liquid nitrogen or dry ice/ethanol bath quick freezing.

7.SDS-PAGE dye or the expression of three site mutation rhIL-2 is analyzed in coomassie brilliant blue staining and Western-blot activation analysis with silver.

8. require three site mutation rhIL-2 are carried out electrophoretic separation according to SDS-PAGE.

9. electrotransfer

By electric current the protein transduction in the gel phase is moved on on the cellulose nitrate film.After gel taken out in the sheet glass, gel is close on the cellulose nitrate film that electricity consumption transfering buffering liquid in advance soaks 30 minutes.With sandwich method filter paper, gel, cellulose nitrate film, filter paper are docile and obedient preface and put well, fix with sponge cloth, sieve tray then, insert in the electrotransfer groove, and add transfering buffering liquid, guarantee gel at negative electrode, NC film in anode direction.The electrotransfer condition is 90 volts, 2 hours, and 4 ℃.The electrotransfer operation does not have bubble to appear inside.

10. after electrotransfer finishes, place 10mL to the suitable confining liquid of NC film the NC film, be placed in the vinyl disc, place on the shaking table and rotate, about 1 time/second, shake 30min.After this step sealing, discard confining liquid.

11. with 20mL distilled water rinsing film 5min, discard water then, repetitive operation once.

12. film is placed on 10mL one anti-damping fluid, hatched 1 hour and the first antibody reaction, discard solution then for 37 ℃.

13. the antibody washing lotion with the 20mL dilution is washed film 5min, discards washing lotion, repetitive operation three times.

14. film is placed on 10mL two anti-damping fluids, hatch 30min for 37 ℃, with the enzyme-labeled secondary antibody reaction, discard solution then.

15. wash film 5min with 20mL antibody washing lotion, discard washing lotion, repetitive operation is more than three times.

16., discard water then with 20mL distilled water rinsing film 2min.Repeat twice.

17. film is placed on to hatch up to the purple band in the 5mL chromogenic substrate damping fluid appears on the film.This variation can be finished in 1～60min.

18., discard water then with 20mL distilled water rinsing film 2min.Repeat twice.

Dry up in air 19. film is placed on the clean filter paper, also can by a branch of dry up or place under the infrared lamp through little warm air dry, result such as Fig. 4.

Example II

One, the purifying of three site mutation rhIL-2 and determination of activity

More the purifying of relevant rhIL-2 is limited to from intestinal bacteria and extracts, with pichia pastoris phaff express and purifying secreted type is natural and mutant rhIL-2 still first, purifying three site mutation rhIL-2 are brand-new heuristic process from this expression system.It is the simplest that we have groped a cover, fast purification step.

Behind the methanol induction 3 days, 4 ℃, the centrifugal 10min of 15000rpm, supernatant liquor add inhibitor PMSF to 1mmol/L or 5～10mmol/L EDTANa of serine protease immediately ₂, prevent the effect of proteolytic enzyme ,-20 ℃ are frozen.Therefore the volume of the fermented liquid of secretion type expression product is very big, but concentration is lower, must concentrate before purifying, operate at refrigerator during purifying, supernatant liquor with 0.45 μ m membrane filtration in case molecule filter membrane is stopped up.Obtain the fermented supernatant fluid 200mL that gets ready after the filtration, dam with the film of MW=30000, add the fermented liquid distilled water that is equivalent to 5 volumes, circulation filters, and discards concentrated solution seldom in the cup at last.Remove MW greater than 30000 impurity.Collection contains the filtered liquid of three site mutation rhIL-2, and lyophilize is concentrated into 200mL, electrophoresis detection.

Film with MW=10000 dams again, add about 5～10 volumes of acetate-sodium acetate buffer of 50mmol/L, pH3.5, the filtered solution in the cup is replaced to damping fluid, concentrate into about 200mL or still less, it is also concentrated less than 10000 impurity to remove MW, gets trace and carries out electrophoresis detection.Remaining be used for ion-exchange.We select strong cat ion exchange column for use ion-exchange chromatography, pH3.5, three site mutation rhIL-2 are soluble under this pH, and most of pichia pastoris proteins can not be adsorbed onto on this resin, good purification effect can be obtained, three site mutation rhIL-2 of 85% purity can be obtained behind the wash-out.This class of gel exclusion chromatography is separated small scale, the slow operating unit of velocity of separation is placed at last, can improve separating effect like this.Gel filtration chromatography is placed on final step and not only plays the result who is further purified, and can transit directly in the suitable buffer system, is beneficial to product shaping and preserves.We select the final step of SephadexG-100 molecular sieve column chromatography as purifying three site mutation rhIL-2 for use, size according to molecular weight is carried out separation and purification, can obtain three site mutation rhIL-2 of 95% above purity through gel permeation chromatography, as shown in Figure 4.Its operating process is as follows:

1. the fermented liquid of handling well that contains three site mutation rhIL-2;

2. the effect group of selecting for use Bio-Rad company to provide is-SO ₃ ^-Storng-acid cation exchange resin, the acetate of 50mmol/L PH3.5-sodium acetate buffer balance cylinder, cylinder size: 2.5 * 30cm;

3. the fermented liquid of handling well that contains three site mutation rhIL-2, the acetate of 50mmol/L PH3.5-sodium acetate buffer flushing makes three site mutation rhIL-2 in conjunction with the S post simultaneously;

4. acetate-the sodium acetate buffer that contains 0～1mol/L NaCL with 50mmol/L carries out the continuous gradient wash-out;

5. collection contains three site mutation rhIL-2 elutriants, and there is the position electrophoresis detection in it;

6. desalination, the sample after the lyophilize is dissolved in the ammonium acetate buffer of a small amount of pH7.0,0.1mol/L;

7. go up the SephadexG-100 chromatography column, column type 1.5 * 80cm;

8. pillar is through including 5mmol/LEDTANa ₂, the NH of 2mmol/L mercaptoethanol, 0.1mol/L pH7.0 ₄The balance liquid equilibrate overnight of Ac damping fluid.Behind the last sample, carry out wash-out with above-mentioned balance liquid;

9. collection contains three site mutation rhIL-2 elutriants, and there is the position electrophoresis detection in it;

10. get an amount of Eppendof pipe, 96 porocyte culture plates etc. are done respective markers;

11. preparation cell suspension: collect the CTLL-2 cell, wash each centrifugal 5min of 2000rpm 3 times with the basic culture solution that RPMI-1640 adds 10% calf serum or do not have a newborn calf serum configuration of mycoplasma;

Be made into 5.0 * 6.0 * 10 with basic culture solution ⁵The cell suspension of/mL,

Place under 37 ℃ of conditions preserve standby;

12. preparation sample solution: get a standard substance by specification and be made into standard model solution.The detected sample by specification of getting specified quantity is made into sample solution to be checked;

13. preparation sample solution: with basic culture solution with the standard model solution dilution to 200IU/mL.According to circumstances with basic culture solution with three site mutation rhIL-2 solution dilutions to be checked to about 200IU/mL, per step must not dilute above 10 times.Solution by above pre-dilution program preparation is called sample solution;

14. preparation sample gradient: in 96 porocyte culture plates, every hole adds 50 μ L complete culture solutions.Add 50 μ L standard solutions in each hole, A4～6, in A1～3, A7～9, every hole adds 50 μ L, three site mutation rhIL-2 solution in each hole, A10～12, and each sample to be checked is done 3 multiple holes, and capable of the capable doubly dilution of opposing of H from A, the surplus liquid of 50 μ L is stayed in every hole.Wherein H4～6 three holes give over to blank;

15 add cell suspension and cultivation: every hole adds 50 μ L cell suspensions, 37 ℃, 5%CO ₂Cultivated under the condition 18～24 hours, to H4～6 10% of the not enough A4 of each hole survivaling cell～6 each hole;

Second day

16. add MTT solution and cultivation: every hole adds 20 μ LMTT solution, 37 ℃, 5%CO ₂Cultivated under the condition 4～6 hours;

17. adding is made into 15% analytical pure sodium dodecyl sulfate solution as lysate and insulation with distilled water.Every hole adds 150 μ L lysates, is incubated 18～24 hours under 37 ℃ of conditions;

The 3rd day

18. measure the OD value: colorimetric on microplate reader, measure wavelength 570nm, reference wavelength 690nm, record measurement result such as Fig. 5;

19. the available energy as a result of biologic activity detection method induces the highly diluted concentration of the testing sample of 50% maximum reaction to tire as a reference or titre, being 1 unit with the amount that is comprised cytokine in this extent of dilution perhaps, is the contained units of institute's factor-containing in the testing sample with this dilution inverse promptly.Usually calculate the activity unit or the concentration of testing sample with direct graphing method.Extent of dilution with IL-2 standard substance and three site mutation rhIL-2 testing samples is an X-coordinate, and the OD value of the mensuration of MTT is the ordinate zou mapping.50% place in the maximum OD value of IL-2 standard substance makes a straight line parallel with X-coordinate, this straight line and each curve have joining, joining is made vertical line to X-coordinate respectively, obtain IL-2 standard substance and each three site mutation rhIL-2 testing sample with the corresponding extent of dilution of 50% maximum OD value.The natural IL-2 of three site mutation rhIL-2 specific activitys that measures with Fig. 6 method is active high about 4.3 times.

Activity unit: U/mL

Claims (2)

1. a recombinant human interleukin--2 Trimutant is characterized in that changing 18 leucines of natural human interleukin II into methionine(Met), and 19 leucines change Serine into, 125 halfcystines change L-Ala into.

2. a recombinant human interleukin--2 Trimutant preparation method is characterized in that:

(1) design of primers

Design 4 nucleotide primers: primer 1,5 ' GCGAATTCTCAAGTCAGTGTTGAGATGATGCTTTGCGCAAAGG 3 ', primer 2,3 ' CTGTAAATCAGACAATTAAATG5 ', primer 3,5 ' GCACGTTACGTAAGCACCTACTTCAAGTTCTAC 3 ', primer 4,5 ' GCATTTAATGTCTGATTTACAG 3 ', wherein primer 1 and primer 4 are one group, primer 2 and primer 3 are one group, with natural human interleukin II cDNA is that template is carried out PCR, preceding two groups PCR product is merged, the PCR product that is combined with primer 1 and primer 3 carries out PCR the 3rd time, contain EcoR I restriction enzyme site in the primer 1, termination codon, 125 Cys change a complementary sequence of Ala and ripe human IL-2's 3 ' terminal portions amino acid encoding gene into, primer 2, primer 3 contains SnaB I restriction enzyme site, initiation codon and ripe human IL-2's 5 ' terminal portions amino acid coding, primer 4 is a mutant primer, wherein 18,19 leucines are mutated into 18 Met and 19 Ser respectively, through behind 3 PCR, obtain three site mutation Human Inter Leukin-2s' dna fragmentation, the low melting-point agarose electrophoresis reclaims the 0.4kb band, and the PCR product that finally obtains is for containing SnaB I and EcoR I restriction enzyme site and 18, the IL-2DNA fragment of 19 and 125 sudden changes;

(2) subclone

Three site mutation Human Inter Leukin-2s' dna fragmentation is cut with SnaB I and EcoR I enzyme, reclaimed, be cloned into then in the pPIC9K eukaryon expression plasmid, transform TOP10F ' bacterial strain, the amplification of firm back obtains Ppic9K- ¹⁸Met- ¹⁹Ser- ¹²⁵Ala-rhIL-2 plasmid, sequencing result prove that 18 CTG have changed ATG into as shown in Figure 2, and 19 CTG have changed TCT into, and 125 TGT have changed GCG into, are the three site mutation human interleukin-12s that we need;

(3) conversion, abduction delivering

Then with Ppic9K- ¹⁸Met- ¹⁹Ser- ¹²⁵The Ala-rhIL-2 plasmid transforms the KM71 pichia pastoris phaff, and obtaining host cell is pichia pastoris phaff KM71/Ppic9K- ¹⁸Met- ¹⁹Ser- ¹²⁵Ala-rhIL-2 by this host cell of inducing culture, obtains three site mutation Human Inter Leukin-2 albumen from its fermented supernatant fluid.

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