532 results about "Asparagine" patented technology

The invention discloses a formate dehydrogenase mutant and application thereof in catalytic synthesis of D-mannitol, and belongs to the technical field of bioengineering. According to the formate dehydrogenase mutant provided by the invention, the 18th-site glutamic acid of wild-type formate dehydrogenase with an amino acid sequence shown as SEQ ID NO.2 is mutated into proline, the 57th-site asparagine is mutated into glutamic acid, the 70th-site histidine is mutated into tryptophan, the 235th-site serine is mutated into threonine, and the 316th-site valine is mutated into threonine, so that the formate dehydrogenase mutant is high in enzyme activity and catalytic activity; the coenzyme circulation efficiency during the production of D-mannitol can be obviously improved, so that the yield of D-mannitol can be effectively improved. When the genetically engineered bacterium co-expressed by the formate dehydrogenase mutant and the mannitol dehydrogenase mutant is used for catalyzing 150 g / L fructose to produce D-mannitol, the yield of D-mannitol within 15 h can reach 140 g / L or above.

The invention discloses a high-performance carbonyl reductase mutant and application thereof in synthesis of a series of chiral alcohols. The high-performance carbonyl reductase mutant is obtained by performing the following mutations on an amino acid sequence as shown in SEQ ID NO.2: the 69th alanine mutates into any one of lysine, leucine, aspartic acid or asparagine, and the 69th alanine mutates into any one of lysine, leucine, aspartic acid or asparagine; and / or the 100th glycine is mutated into any one of glutamic acid, serine, lysine or asparagine. Compared with a wild type enzyme, the thermal stability and the catalytic activity of the obtained mutant are remarkably improved, particularly, single point mutants Mut-A69N, Mut-G100E and Mut-G100N and a combined mutant Mut-A69N-G100N show excellent relative enzyme activity, thermal stability and substrate tolerance. The mutant has high catalytic activity and stability to various chiral alcohols, and the contradiction that the traditional carbonyl reductase is easy to inactivate at high temperature and the catalytic efficiency is difficult to achieve at the same time is solved. The invention provides an efficient and stable enzyme catalysis tool for green biological preparation of chiral drug intermediates.

The invention relates to the field of polypeptide compositions, in particular to a polypeptide metal chelate and application thereof in the field of cosmetics, and the polypeptide metal chelate is formed by chelating a polypeptide compound and a metal ion compound. The structure of the polypeptide compound is [gamma-Glu] n-AA, n is greater than or equal to 1, and AA is selected from glycine, alanine, valine, leucine, isoleucine, methionine (methionine), proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, asparaginic acid, glutamic acid, lysine, arginine or histidine; the polypeptide chelated zinc prepared by the invention has remarkable oil control and anti-inflammatory effects, and can be compounded with other raw materials to form cosmetics with oil control and acne removal effects.

The invention provides an SNP (Single Nucleotide Polymorphism) mutation site associated with turbot blackening, a molecular marker and application, and belongs to the technical field of molecular markers. According to the SNP locus related to turbot blackening, the SNP locus related to turbot blackening is found through pathway analysis, SNP locus screening, SNP locus typing and SNP locus screening related to turbot non-eye side body color blackening, the SNP locus is located on a gene tyrosinase-related protein 1b, a base G at the 835bp position is mutated into A, aspartic acid can be changed into asparagine, and the non-eye side of turbot is not prone to blackening. When scophthalmus maximus breeding is carried out, the breeding scophthalmus maximus can be subjected to pre-breeding molecular screening by using the SNP site associated with the body color blackening of the non-eye side of the scophthalmus maximus, so that the occurrence rate of the non-eye side blackening of the progeny of the scophthalmus maximus is reduced from germplasm, and the blackening phenomenon in the breeding process of the scophthalmus maximus is reduced.

The present invention discloses a complete medium for culturing DF-1 cells, including DMEM basal medium 13.7g / L, insulin, non-essential amino acids, transferrin, glutathione, ascorbyl phosphate, sodium selenite, ethanolamine, hydrocortisone, and newborn calf serum. Wherein non-essential amino acids include glycine, alanine, proline, serine, and asparagine. A complete medium for culturing DF-1 cells provided by the present invention can well promote the proliferation of DF-1 cells, can achieve the same proliferation effect as high-concentration fetal bovine serum, and is suitable for the adherent culture of DF-1 cells; using low-concentration newborn calf serum, it is possible to greatly avoid the batch differences, unstable culture results, cytotoxicity, and high risk of carrying pathogens brought by the culture medium with high-concentration serum, narrow application range, expensive fetal bovine serum, and high culture cost; the components are simple, the culture medium preparation process is short in time consumption, the culture efficiency is high, the repeatability is good, and it is suitable for batch production.

The invention discloses a gelator and a preparation method and application thereof, the structural formula of the gelator is # imgabs0 #, R1 is a side chain group connected to an amino acid central carbon atom except an amino group, a carboxyl group and a hydrogen atom; the amino acid is selected from one of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine and pyrrole lysine; the amino acid is selected from one of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine and pyrrole lysine; r2 is alkyl with the carbon atom number of 16 to 19; and R3 is 9-fluorenyl methoxy carbonyl group or t-butyloxycarbonyl group. The gelator has a hydrophobic long alkyl tail chain, can spontaneously gather and assemble into a three-dimensional network structure through hydrogen bonds, pi-pi interaction and hydrophobic force, and fixes an oil phase in an oil solvent or an oil-water mixture in an effective manner to form high-strength gel.

The invention relates to a high-temperature-resistant saccharomyces cerevisiae strain and a construction method and application thereof in the field of microorganisms. The high-temperature-resistant saccharomyces cerevisiae strain disclosed by the invention is preserved in the China General Microbiological Culture Collection Center (CGMCC), the preservation number is CGMCC NO.27605, and the preservation name is SEB22. The SEB22 bacterial strain is obtained by knocking out an L-asparaginase II coding gene ASP3 and a high-expression transcription factor CRZ1 from an original bacterial strain SEB4. The glucose consumption rate, the ethanol yield and the yield of the SEB22 strain under high-temperature stress are obviously improved, and the SEB22 strain has good application potential in the aspect of high-temperature SSF fermentation.

The present application relates to a pyridoxal kinase mutant, a recombinant expression vector and a microbial cell and their applications, and belongs to the technical field of biological catalysis. In order to solve the problem of low product concentration in existing enzyme catalysis, a pyridoxal kinase mutant is provided, the amino acid sequence is selected from the amino acid sequence shown in SEQ ID NO. 1, the lysine at position 229 is mutated to alanine, phenylalanine, methionine, arginine, threonine, histidine, serine, tyrosine, valine, leucine, isoleucine, proline, asparagine, aspartic acid or glutamic acid; the pyridoxal kinase mutant is used for catalyzing pyridoxal to synthesize pyridoxal phosphate, and a recombinant expression vector and a microbial cell can be further formed. The present application has good enzyme activity, high product conversion rate, high concentration of pyridoxal phosphate obtained, and the concentration of the product catalyzed by the wild-type pyridoxal kinase to phosphorylate pyridoxal is obviously improved.

The invention discloses an Escherichia coli endogenous alcohol dehydrogenase EcYjgB mutant and application thereof. The mutant is obtained by performing any one of the following mutations (a) to (c) on Escherichia coli endogenous alcohol dehydrogenase EcYjgB as shown in SEQ ID NO.1: (a) mutating serine at the 200th site into arginine; (b) the serine at the 199th site is mutated into aspartic acid, and the serine at the 200th site is mutated into arginine; and (c) the serine at the 199th site is mutated into aspartic acid, the serine at the 200th site is mutated into arginine, and the asparagine at the 240th site is mutated into tryptophan. The mutant is used for efficiently catalyzing reduction of HMF or furfural to respectively synthesize BHMF and furfuryl alcohol, so that the purposes of improving the production efficiency, reducing the production cost and improving the environmental effect are achieved.

The invention provides a T7-RNA polymerase mutant capable of reducing generation of dsRNA and application of the T7-RNA polymerase mutant, tryptophan at the 328th site from the N terminal of an amino acid sequence of wild type T7-RNA polymerase is substituted by methionine, phenylalanine, asparagine, alanine or lysine, and a by-product dsRNA generated in an in-vitro transcription process can be reduced. Through computer simulation, a large amount of screening work is reduced, the enzyme evolution speed is increased, and the cost and time of enzyme modification are greatly reduced; the T7-RNA polymerase mutant maintains efficient transcription, reduces the complexity of later purification work, reduces the purification cost of RNA production, can quickly prepare RNA drugs meeting the use requirements, and provides an efficient tool enzyme for large-scale production of the RNA drugs.

The invention discloses a rice ACCase mutant protein and a preparation method thereof. The amino acid sequence of the ACCase mutant gene encoding protein has the following mutations: the 2052nd site corresponding to the amino acid sequence of wild rice ACCase is mutated, isoleucine (I) is changed into asparagine (N), or isoleucine (I) is changed into glutamine (Q), or isoleucine (I) is changed into cysteine (C), or isoleucine (I) is changed into cysteine (C), or isoleucine (I) is changed into cysteine (C), or isoleucine (I) is changed into cysteine (C), or isoleucine (I) is changed into cysteine (C). And the plant can have extremely strong resistance (tolerance) to acetyl-coenzyme A carboxylase inhibitor herbicides. After the rice containing the rice ACCase mutant protein disclosed by the invention is applied with an acetyl-coenzyme A carboxylase inhibitor herbicide with 8 times of recommended use concentration, plants still grow normally, and the tolerance of the herbicide is greatly enhanced, so that the rice ACCase mutant protein can be widely applied to breeding of herbicide-resistant plants.

In the first aspect, the present disclosure provides a Lactoferrin polypeptide fragment, where the Lactoferrin polypeptide fragment has an amino acid sequence shown in SEQ ID NO: 1. In the second aspect, the present disclosure provides a preparation method of the Lactoferrin polypeptide fragment, including: protecting amino acids using a 9-fluorenylmethoxycarbonyl (Fmoc) protecting group, coupling the amino acids with a P-hydroxymethylphenoxymethyl polyethylene resin (HMP resin) in an order of cysteine, alanine, leucine, cysteine, glutamate, threonine, asparagine, aspartate, asparagine, phenylalanine, leucine, leucine, asparagine, and lysine, and separating the HMP resin to obtain a target Lactoferrin polypeptide fragment. In the third aspect, the present disclosure further provides an anti-Lactoferrin antibody prepared using the Lactoferrin polypeptide fragment, and use of the Lactoferrin polypeptide fragment in preparation of an anti-Lactoferrin flow cytometric antibody and in preparation of a Lactoferrin detection product.

The invention belongs to the technical field of biology, and particularly relates to a CHO cell suspension culture medium as well as a preparation method and application thereof. The culture medium comprises amino acids, vitamins, inorganic salts, trace elements, carbohydrates and other molecular compounds; the amino acids comprise glycine, L-alanine, L-arginine, L-asparagine, L-aspartic acid, L-cysteine, L-cystine, L-glutamic acid, L-histidine, L-isoleucine, L-leucine, L-lysine, L-methionine, L-phenylalanine, L-proline, L-serine, L-threonine, L-tryptophan, L-tyrosine and L-valine. The culture medium provided by the invention can meet the high-density suspension culture of various CHO cells, can improve the production efficiency and reduce the production cost, and has wide application prospects and values. The culture medium provided by the invention overcomes the defects of the existing culture medium with determined chemical components, and provides more choices for the culture medium with determined chemical components in China.

The invention is suitable for the technical field of soybean breeding, and provides a KASP molecular marker for soybean plant height identification and application of the KASP molecular marker. The KASP molecular marker is based on an SNP variation site of a Glyma. 19G206100 gene between two parents of Chinese flat stem soybean and F02, the mutation position of the Glyma. 19G206100 gene is the 312th basic group on a CDS sequence, C of a reference genome is mutated into G, the 104th amino acid on a protein sequence is mutated into lysine from asparagine, and the 104th amino acid on the protein sequence is mutated into lysine from asparagine. The primer of the KASP molecular marker comprises a forward primer with a nucleotide sequence as shown in SEQ ID NO.1-2 and a reverse primer with a nucleotide sequence as shown in SEQ ID NO.3. The invention further discloses a kit for detecting the KASP molecular marker. The KASP molecular marker is developed on the basis of the polymorphic site of Gm19G206100 in germplasm resources, the marker has the advantages of being high in resolution ratio and easy to detect, can be applied to plant height selection of early generations of soybean cross breeding, has the effects of reducing the breeding scale, reducing the workload and improving the breeding efficiency, and has important application value in production.

According to the scheme, the invention provides the recombinant macrolide enzyme as well as the preparation method and the application thereof, the amino acid sequence of the recombinant macrolide enzyme is as shown in SEQ ID NO.1, and the recombinant macrolide enzyme is derived from an EreC esterase family of enterobacter hormaechei and is obtained through site-specific mutagenesis; the mutation sites are as follows: glutamic acid at the 44th site is mutated into asparagine, tyrosine at the 55th site is mutated into proline, proline at the 76th site is mutated into arginine, phenylalanine at the 153rd site is mutated into alanine, and serine at the 219th site is mutated into glutamic acid. The method is expected to remove macrolide antibiotic pollution, and has good economic benefits and practical values.

The present invention relates generally to glutamine-free cell culture media supplemented with asparagine. The invention further concerns the production of recombinant proteins, such as antibodies, in asparagine-supplemented glutamine-free mammalian cell culture.

The invention relates to a pyridoxal kinase mutant, a recombinant expression vector, a microbial cell and application thereof, and belongs to the technical field of biological catalysis. In order to solve the problem of low concentration of the existing enzyme catalysis product, the invention provides the pyridoxal kinase mutant. The amino acid sequence is selected from lysine at the 229 site of the amino acid sequence as shown in SEQ ID NO.1, and the lysine at the 229 site of the amino acid sequence as shown in SEQ ID NO.1 is mutated into alanine, phenylalanine, methionine, arginine, threonine, histidine, serine, tyrosine, valine, leucine, isoleucine, proline, asparagine, asparaginic acid or glutamic acid; the pyridoxal kinase mutant is used for catalyzing pyridoxal to synthesize pyridoxal phosphate, and recombinant expression vectors, microbial cells and the like can be further formed. The pyridoxal phosphate has good enzyme activity and high product conversion rate, the concentration of the obtained pyridoxal phosphate is high, and the concentration of a product obtained by catalyzing phosphorylation of pyridoxal through the pyridoxal phosphate kinase is obviously improved compared with that of a product obtained by catalyzing phosphorylation of pyridoxal through wild type pyridoxal kinase.

The invention relates to a chicken beta-defensin-6 mutant based on AI aided design, a recombinant expression system and application, and relates to the technical field of gene engineering and protein engineering. The chicken beta defensin-6 mutant has the following amino acids at the following five sites: lysine at the 33rd site, lysine at the 35th site, asparagine at the 49th site, arginine at the 61st site and proline at the 65th site. The chicken beta-defensin-6 mutant has high stability, activity and solubility, compared with wild chicken beta-defensin-6, the chicken beta-defensin-6 mutant has higher antibacterial activity and expression level, an efficient and safe antibacterial substitute is provided for livestock and poultry breeding, and the chicken beta-defensin-6 mutant can be widely applied to the fields of livestock and poultry breeding, animal health care and biological preservation.

In order to improve aggregation property of a PPR protein, the A6 amino acid of the 1st PPR motif from the N-terminus (M1) is made more hydrophilic. Further, the A9 amino acid of M1 is made to be a hydrophilic amino acid or glycine. The A6 amino acid is preferably asparagine or aspartic acid, and the A9 amino acid is preferably glutamine, glutamic acid, lysine, or glycine. Proteins containing such a PPR motif as M1 motif may have not only improved aggregation property, but also high binding power to a target nucleic acid.

The invention discloses a fermentation process for shortening a fermentation period and efficiently synthesizing Ectoine. The fermentation process comprises the following steps: screening and activating high-yield strains, preparing a fermentation culture medium, performing fermentation culture, performing sectional dissolved oxygen regulation and control, performing double-stage pH dynamic regulation and control, performing carbon-nitrogen ratio dynamic regulation based on metabolic flow analysis, performing osmotic pressure gradient induction in the later stage of fermentation, and extracting and purifying a product. According to the fermentation process for shortening the fermentation period and efficiently synthesizing the Ectoin, the expression quantity of key enzymes for synthesizing the Ectoin is increased by 80% or above compared with that of an original strain through the Halomonassp.ECT-09 strain bred through ultraviolet-nitrosoguanidine compound mutation, the basic yield reaches 35 g / L, a foundation is laid for high yield, and the method is suitable for industrial production. A glucose-trehalose mixed carbon source and a yeast extract-ammonium nitrate mixed nitrogen source are adopted, and an L-aspartic acid-L-asparagine mixed precursor is added, so that the metabolic pathway is shortened, and the loss of an intermediate product is reduced.

Disclosed herein is a delivery agent that facilitates effective delivery of drugs and other compounds across lipid layers. The delivery agent disclosed herein comprises an asparagine-containing mask peptide group comprising at least one asparagine amino acid moiety and which provides lipid solubility under selected conditions and aqueous solubility under other conditions, and can effectively deliver compounds into the cell cytosol.

The invention provides an acrylamide generation inhibitor and a method for inhibiting acrylamide generation. The acrylamide inhibitor is syringic acid, vanillic acid or sinapic acid. The syringic acid and the vanillic acid can passivate polyphenol oxidase in the food processing process and prevent polyphenol oxidase from oxidizing polyphenol in food into quinone, and the sinapic acid can directly inhibit quinone generated by oxidizing polyphenol, so that the content of Maillard reaction substrates is reduced, and the yield of the Maillard reaction products is improved. The structure of quinone is extremely similar to that of an intermediate product dicarbonyl compound in a path for producing acrylamide through Maillard reaction, so that quinone and asparagine can be subjected to Maillard reaction under a high-temperature condition to generate acrylamide. Therefore, the Maillard reaction is prevented by passivating the activity of polyphenol oxidase or inhibiting the generation of quinone oxidized by polyphenol, the generation of 2A cancerogen acrylamide easily generated in the high-temperature food processing process is further inhibited, the purpose of healthy diet is achieved, and a new thought is provided for controlling the generation of acrylamide in the food processing process.

The present invention relates to an isolated peptide comprising the amino acid sequence of Formula (I): (O)n-K-(O)m-Z; wherein K is lysine optionally modified with a self-immolative moiety Z is tryptophan or is absent; O is GHGX1Y (SEQ ID NO: 1); G is glycine, H is histidine, Y is tyrosine; each X1 is independently selected from alanine, glycine, serine, asparagine, histidine (H), arginine (R), aspartic acid, tyrosine, and proline; n is 0 – 5; m is 0 – 5; n+m is 3, 4, 5, 6, 7 or 8, and optionally, wherein not all of the X1 residues are proline (P). Such peptide is a coacervate forming peptide. The present invention also relates to methods of preparing coacervate compositions comprising the isolated peptide, optionally also comprising one or more biomacromolecules (payloads). The present invention further relates to the coacervate compositions per se, and their uses, e.g. in methods of treatment or diagnosis.

The invention discloses a carbonyl reductase mutant for synthesizing a chiral alcohol sulfone compound and application of the carbonyl reductase mutant, a mutant M4A1 of carbonyl reductase ChKRED20 is used as a female parent, serine at the 188th site is mutated into any one of asparagine, glycine or threonine, and the carbonyl reductase mutant for synthesizing the chiral alcohol sulfone compound is obtained. Specifically, a mutant M4A1 of ChKRED20 is taken as a female parent, serine at the 188th site is mutated into asparagine, and a mutant ChKRED20-M4C4 is obtained. The mutant M4A1 of ChKRED20 is used as a female parent, serine at the 188th site is mutated into glycine, and the mutant ChKRED20-M4C3 is obtained. The mutant M4A1 of ChKRED20 is used as a female parent, serine at the 188th site is mutated into threonine, and the mutant ChKRED20-M4C6 is obtained. The three mutants can be used as catalysts to synthesize chiral alcohol sulfone compounds, and especially have great advantages in asymmetric synthesis of alpha-substituted beta-alcohol sulfone.

The invention provides a lipid nanoparticle conjugate as well as a preparation method and application thereof. In particular, an antibody is coupled to the surface of the LNP through an N-glycosylation site of an Fc heavy chain by using a copper-free click chemical reaction, thereby obtaining the LNP having a specific cell or tissue targeting property. Preferably, the N-glycosylation site is located on the asparagine residue at the 297th position of the Fc heavy chain.

The invention relates to the technical field of agricultural biology, in particular to ALS inhibitor broad-spectrum resistance mutant protein and application. According to the invention, a gene editing technology is utilized to edit rice ALS genes, then resistance screening is carried out to obtain two new rice ALS mutant proteins, and compared with rice wild-type ALS proteins, the ALS mutant proteins have the advantages that the rice ALS mutant proteins have higher rice ALS mutant proteins; the mutation comprises the mutation that the 171st proline is mutated into threonine, the 172nd arginine is mutated into glycine and the 174th methionine is mutated into leucine, or the mutation comprises the mutation that the 169th glutamine is mutated into asparagine and the 170th valine is mutated into glutamine. The two mutant proteins are reported for the first time, so that rice has relatively high resistance to various ALS inhibitor herbicides; meanwhile, the mutant gene can be used as a plant endogenous transgenic selection marker and added with other functional elements for plant gene transformation, and has great value in commercial application of transgenic plants.

The invention belongs to the technical field of biological medicines, and particularly relates to application of asparaginase in preparation of a medicine for treating pancreatic cancer. The asparaginase and the gemcitabine are combined for treating pancreatic cancer, and results show that the combination of the two medicines can promote apoptosis of pancreatic cancer cells, reduce proliferation and reduce activation of pancreatic stellate cells, so that an important scientific basis is provided for improving gemcitabine drug resistance, and meanwhile, a new application is provided for the asparaginase.

There is provided peptidic compounds of Formula I, A or B(Rradn6-[linker]-RL-Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-ψ-Xaa9-NH2). Xaa1 is D-Phe, Cpa, D-Cpa, Nal, D-Nal, 2-Nal, or D-2-Nal; Xaa2 is Asn, Gln, Hse, Cit or His. Xaa3 is Trp, Bta, Trp(Me), Trp(7-Me), Trp(6-Me), Trp(5-Me), Trp(4-Me), Trp(2-Me), Trp(7-F), Trp(6-F), Trp(5-F), Trp(4-F), Trp(5-OH), or αMe-Trp. Xaa4 is Ala or Ser. Xaa5 is Val, Cpg, or Tle. Xaa6 is Gly, NMe-Gly, or D-Ala. Xaa7 is His or NMe-His. Xaa8 is Leu or Phe. Xaa9-NH2 is a C-terminally amidated amino acid residue selected from Pro, 4-oxa-L-Pro, Me2Thz, or Thz. ψ represents a peptide bond or reduced peptide bond joining Xaa8 to Xaa9. Rradn6 is 1-5 radiolabeling groups. There is also provided the use of such compounds as imaging agents or therapeutic agents.

The present invention belongs to the technical field of enzyme engineering, and discloses a Microbacterium dextranolyticum β-glucosidase mutant, which is obtained by mutating the 329th position of the β-glucosidase of the amino acid sequence as shown in SEQ ID NO.1 from glutamic acid to glycine; or, mutating the 329th position of the β-glucosidase of the amino acid sequence as shown in SEQ ID NO.1 from glutamic acid to asparagine; or, mutating the 329th position of the β-glucosidase of the amino acid sequence as shown in SEQ ID NO.1 from glutamic acid to lysine, and mutating the 72nd position from arginine to asparagine. The present invention solves the technical problems existing in the current enzymatic conversion production of high-value natural products, and obtains a β-glucosidase mutant with improved enzyme activity by site-directed mutagenesis technology.

The present invention relates to an affinity purification system that utilises a polypeptide comprising: (i) an amino acid sequence as set forth in SEQ ID NO: 1, wherein X at position 79 is selected from alanine, glycine, serine, asparagine, or threonine; (ii) a portion of (i) comprising an amino acid sequence as set forth in SEQ ID NO: 2, wherein X at position 56 is selected from alanine, glycine, serine, asparagine or threonine; (iii) an amino acid sequence with at least 80% sequence identity to a sequence as set forth in SEQ ID NO: 1, wherein the polypeptide comprises alanine, glycine, serine, asparagine or threonine at a position equivalent to position 79 of SEQ ID NO: 1; or (iv) a portion of (iii) comprising an amino acid sequence with at least 80% sequence identity to a sequence as set forth in SEQ ID NO: 2, wherein the polypeptide comprises alanine, glycine, serine, asparagine or threonine at a position equivalent to position 56 of SEQ ID NO: 2, wherein the polypeptide binds selectively and reversibly to a peptide comprising an amino acid sequence as set forth in SEQ ID NO: 3, 4 or 5.