Zearalenone is one of the most widely polluted Fusarium toxins in the world, seriously endangering livestock and human health. Zearalenone hydrolase (ZHD) derived from Clonostachys rosea can effectively degrade zearalenone. However, the high temperature environment in feed processing hampers the application of this enzyme. Structure-based rational design may provide guidance for engineering the thermal stability of enzymes. In this paper, we used the multiple structure alignment (MSTA) to screen the structural flexibility regions of ZHD. Subsequently, a candidate mutation library was constructed by sequence conservation scoring and conformational free energy calculation, from which 9 single point mutations based on residues 136 and 220 were obtained. The experiments showed that the thermal melting temperature (T_m) of the 9 mutants increased by 0.4-5.6 ℃. The S220R and S220W mutants showed the best thermal stability, the T_m of which increased by 5.6 ℃ and 4.0 ℃ compared to that of the wild type. Moreover, the thermal half-inactivation time at 45 ℃ were 15.4 times and 3.1 times longer, and the relative activities were 70.6% and 57.3% of the wild type. Molecular dynamics simulation analysis showed that the interaction force at and around the mutation site was enhanced, contributing to the improved thermal stability of ZHD. The probability of 220-K130 hydrogen bond of the mutants S220R and S220W increased by 37.1% and 19.3%, and the probability of K130-D223 salt bridge increased by 30.1% and 12.5%, respectively. This work demonstrated the feasibility of thermal stability engineering strategy where the structural and sequence alignment as well as free energy calculation of natural enzymes were integrated, and obtained ZHD variants with enhanced thermal stability, which may facilitate the industrial application of ZHD.
Humans ; Hydrolases ; Zearalenone ; Trichothecenes ; Gene Library ; Hydrogen Bonding

Tumor is a serious threat to human health. At present, surgical resection, chemoradiotherapy, targeted therapy and immunotherapy are the main therapeutic strategies. Monoclonal antibody has gradually become an indispensable drug type in the clinical treatment of cancer due to its high efficiency and low toxicity. Phage antibody library technology (PALT) is a novel monoclonal antibody preparation technique. The recombinant immunoglobulin variable region of heavy chain (VH)/variable region of light chain (VL) gene is integrated into the phage vector, and the antibody is expressed on the phage surface in the form of fusion protein to obtain a diverse antibody library. Through the process of adsorption-elution-amplification, the antibody library can be screened to obtain the antibody molecule with specific binding antigen as well as its gene sequence. PALT has the advantages of short antibody production cycle, strong plasticity of antibody structure, large antibody yield, high diversity and direct production of humanized antibodies. It has been used in screening tumor markers and preparation of antibody drugs for breast cancer, gastric cancer, lung cancer and liver cancer. This article reviews the recent progress and the application of PALT in tumor therapy.
Humans ; Bacteriophages/genetics* ; Immunoglobulin Variable Region/genetics* ; Gene Library ; Antibodies, Monoclonal/therapeutic use* ; Immunotherapy ; Peptide Library

Single chain antibody fragment (scFv) is a small molecule composed of a variable region of heavy chain (VH) and a variable region of light chain (VL) of an antibody, and these two chains are connected by a flexible short peptide. scFv is the smallest functional fragment with complete antigen-binding activity, which contains both the antibody-recognizing site and the antigen-binding site. Compared with other antibodies, scFv has the advantages of small molecular weight, strong penetration, low immunogenicity, and easy expression. Currently, the most commonly used display systems for scFv mainly include the phage display system, ribosome display system, mRNA display system, yeast cell surface display system and mammalian cell display system. In recent years, with the development of scFv in the field of medicine, biology, and food safety, they have also attracted much attention in the sectors of biosynthesis and applied research. This review summarizes the advances of scFv display systems in recent years in order to facilitate scFv screening and application.
Animals ; Immunoglobulin Variable Region/genetics* ; Immunoglobulin Fragments/metabolism* ; Single-Chain Antibodies/metabolism* ; Peptide Library ; Mammals/genetics*

OBJECTIVE: To establish a new method for synthesizing Lewis blood group antigens, that is, the mimotopes of Lewis blood group antigens were screened by using an alpaca phage display nanobody library. METHODS: We selected mimotopes of the Lewis a (le^a) antigen by affinity panning of an alpaca phage display nanobody library using a monoclonal anti-le^a antibody. Enzyme-linked immunosorbent assay (ELISA) was used to test the affinity of the positive clones for the monoclonal anti-le^a antibody, and the high-affinity positive clones were selected for sequencing and synthesis. Finally, the sensitivity, specificity and reactivity of the synthesized le^a mimotope in clinical samples were verified by ELISA. RESULTS: A total of 96 phage clones were randomly selected, and 24 were positive. Fourteen positive clones with the highest affinity were selected for sequencing. The result showed that there were 5 different sequences, among which 3 sequences with the highest frequency, largest difference and highest affinity were selected for expression and synthesis. The sensitivity and specificity of le^a mimic antigen by ELISA showed that, the minimum detection limit of gel microcolumn assay (GMA) and ELISA method were 25 times different, and the le^a mimic antigen had no cross reacted with the other five unrelated monoclonal antibodies(P<0.001). Finally, 30 clinical plasma samples were analyzed. The mean absorbance of the 15 positive plasma samples was significantly higher than that of the 15 negative plasma samples (P=0.02). However, the positive signal values of the clinical samples were much lower than those of the monoclonal antibodies. CONCLUSION A new method of screening le^a mimic antigen by using alpaca phage nanoantibody library has been established, which is expected to realize the screening of le^a mimotopes, thus realizing the application of high-sensitivity detection methods such as ELISA and chemiluminescence in blood group antibody identification.
Animals ; Antibodies, Monoclonal ; Antineoplastic Agents, Immunological ; Bacteriophages ; Blood Group Antigens ; Camelids, New World ; Enzyme-Linked Immunosorbent Assay/methods* ; Epitopes ; Humans ; Lewis Blood Group Antigens ; Peptide Library

Promoter is an important genetic tool for fine-tuning of gene expression and has been widely used for metabolic engineering. Corynebacterium glutamicum is an important chassis for industrial biotechnology. However, promoter libraries that are applicable to C. glutamicum have been rarely reported, except for a few developed based on synthetic sequences containing random mutations. In this study, we constructed a promoter library based on the native promoter of odhA gene by mutating the -10 region and the bystanders. Using a red fluorescent protein (RFP) as the reporter, 57 promoter mutants were screened by fluorescence imaging technology in a high-throughput manner. These mutants spanned a strength range between 2.4-fold and 19.6-fold improvements of the wild-type promoter. The strongest mutant exhibited a 2.3-fold higher strength than the widely used strong inducible promoter P_trc. Sequencing of all 57 mutants revealed that 55 mutants share a 1-4 bases shift (4 bases shift for 68% mutants) of the conserved -10 motif "TANNNT" to the 3' end of the promoter, compared to the wild-type promoter. Conserved T or G bases at different positions were observed for strong, moderate, and weak promoter mutants. Finally, five promoter mutants with different strength were employed to fine-tune the expression of γ-glutamyl kinase (ProB) for L-proline biosynthesis. Increased promoter strength led to enhanced L-proline production and the highest L-proline titer of 6.4 g/L was obtained when a promoter mutant with a 9.8-fold higher strength compared to the wild-type promoter was used for ProB expression. The use of stronger promoter variants did not further improve L-proline production. In conclusion, a promoter library was constructed based on a native C. glutamicum promoter P_odhA. The new promoter library should be useful for systems metabolic engineering of C. glutamicum. The strategy of mutating native promoter may also guide the construction of promoter libraries for other microorganisms.
Corynebacterium glutamicum/metabolism* ; Gene Library ; Metabolic Engineering ; Promoter Regions, Genetic/genetics*

Ultrashort peptides have higher stability, tissue penetrability, biocompatibility, and less immunogenicity, and are widely applied in biology and medicine. GHK (glycyl-l-histidyl-l-lysine) and GQPR (glycyl-l-glutamyl-l-prolyl-l-arginine) can stimulate collagen renewal and inhibit collagen degradation. GHK and GQPR have been used in cosmetic anti-wrinkle skincare and make-up products. The most common approach for ultrashort peptide production is the solid-phase synthesis, which is eco-unfriendly due to heavy usage of organic chemical reagents during the manufacturing process. Here we report a new approach to the production of ultrashort peptides. Recombinant expression of ultrashort peptides is usually unfeasible because of the short amino acid sequences. A vector pET28a-Trxm harboring the thioredoxin gene was first constructed for subsequent fusion expression. The tandem repeats of GHK and GQPR genes were used as the templates for rolling circle amplification (RCA). The RCA reaction was tuned to incorporate noncanonical nucleotides 5-methylcytosine to obtain long DNA fragments. Gene sequences with various lengths were generated through double digestion of Acc65 Ⅰ and Apa Ⅰ. The resulting digestion products were gel recovered by size (from 500 bp to 1 500 bp) and cloned into pET28a-Trxm to obtain the recombinant vector pET28a-Trxm-(TRSP)_n. The pET28a-Trxm-(TRSP)_n was introduced into E. coli BL21(DE3) to generate a library of Trxm-(TRSP)_n sequences with a controlled distribution of lengths. Through double digestion and sequencing, positive clones with tandem repeats n=1, 2, 3, 4, 6, 7, 8, 9 were obtained. Protein expression results showed protein bands with corresponding molecular weight, and the protein expression level decreased as the tandem repeats increased. The expression level of Trxm-(TRSP)₁ achieved 50% of the total protein, while the expression level of Trxm-(TRSP)₂ was 30% of the total protein. The crude extracts from cell pellets were further treated with enterokinase cleavage, and the supernatants containing (TRSP)₁ were collected after ultrafiltration and then subjected to trypsin cleavage. HPLC analysis indicated that the ultrashort peptides GHK and GQPR were successfully obtained through two-step cleavage. This study may facilitate the commercial production of ultrashort peptides.
Escherichia coli/metabolism* ; Peptides/chemistry* ; Amino Acid Sequence ; Gene Library ; Tandem Repeat Sequences

OBJECTIVE: To screen proteins interacting with ring finger protein 216(RNF216) through yeast two hybrid experiment, and further clarify the role of RNF216 in the pathogenesis of gonadotropin-releasing hormone deficiency. METHODS: A recombinant expression vector pGBKT7-RNF216 was constructed and transformed into yeast Y2HGold, which was hybridized with a human cDNA library in order to screen proteins interacting with RNF216. The interaction was verified in yeast Y2HGold. RESULTS: A recombinant expression vector pGBKT7-RNF216 was successfully constructed and expressed in yeast Y2HGold. Filamin B (FLNB) was identified by yeast two hybrid experiment, and their interaction was verified in yeast Y2HGold. CONCLUSION An interaction between FLNB and RNF216 was identified through yeast two hybrid experiment. RNF216 may affect the proliferation and migration of GnRH neurons by regulating FLNB or FLNB/FLNA heterodimers.
Gene Library ; Gonadotropin-Releasing Hormone/genetics* ; Humans ; Proteins ; Two-Hybrid System Techniques ; Ubiquitin-Protein Ligases/genetics*

Directed evolution is a cyclic process that alternates between constructing different genes and screening functional gene variants. It has been widely used in optimization and analysis of DNA sequence, gene function and protein structure. It includes random gene libraries construction, gene expression in suitable hosts and mutant libraries screening. The key to construct gene library is the storage capacity and mutation diversity, to screen is high sensitivity and high throughput. This review discusses the latest advances in directed evolution. These new technologies greatly accelerate and simplify the traditional directional evolution process and promote the development of directed evolution.
Base Sequence ; Directed Molecular Evolution ; Gene Library ; Mutation ; Proteins/genetics*

Polyphenol oxidase(PPO) is an important antioxidant enzyme in plants. It has the functions of scavenging active oxygen and synthesizing phenols, lignin, and plant protection factors, and can enhance the plant's resistance to stress and resistance to pests and diseases. Our previous research found that Salvia miltiorrhiza PPO gene can positively regulate salvianolic acid B synthesis. In order to further explore the mechanism, a pGBKT7-PPO bait vector was constructed using the cloned S. miltiorrhiza polyphenol oxidase gene(SmPPO, GenBank accession number: KF712274.1), and verified that it had no self-activation and no toxicity. The titer of S. miltiorrhiza cDNA library constructed by our laboratory was 4.75 × 107 cfu·mL~(-1), which met the requirements for library construction. Through yeast two-hybrid test, 22 proteins that could interact with SmPPO were screened. Only yeast PAL1 and TAT interacted with SmPPO through yeast co-transformation verification. Further verification was performed by bimolecular fluorescence complementary detection(BiFC). Only TAT and SmPPO interacted, so it meant that TAT and SmPPO interacted. TAT and SmPPO were truncated according to the domain, respectively. The first 126 amino acids of SmPPO and tyrosine amino transferase(TAT) were obtained to interact on the cell membrane and chloroplast. SmPPO was obtained by subcellular localization test, which was mainly loca-lized on the nucleus and cell membrane; TAT was localized on the cell membrane. Real-time quantitative PCR results showed that the SmPPO gene was mainly expressed in roots and stems; the TAT gene was expressed in roots, and the expression level in stems and flowers was low. This article lays a solid foundation for the in-depth study of the molecular mechanism of the interaction of S. miltiorrhiza SmPPO and TAT to regulate the synthesis of phenolic substances.
Catechol Oxidase ; Gene Expression Regulation, Plant ; Gene Library ; Plant Proteins ; genetics ; Plant Roots ; Salvia miltiorrhiza ; genetics

Lanosterol synthase( LS) is a key enzyme involving in the mevalonate pathway( MVA pathway) to produce lanosterol,which is a precursor of ganoderma triterpenoid. And the transcriptional regulation of LS gene directly affects the content of triterpenes in Ganoderma lucidum. In order to study the transcriptional regulation mechanism of LS gene,yeast one-hybrid technique was used to screen the transcription regulators which interact withthe promoter of LS. The bait vector was constructed by LS promoter,then the vector was transformed yeast cells to construct bait yeast strain. One-hybrid c DNA library was constructed via SMART technology. Then the c DNA and p GADT7-Rec vector were co-transformed into the bait yeast strain to screen the upstream regulatory factors of the promoter region of LS by homologous recombination. Total of 23 positive clones were screened. After sequencing,blast was performed against the whole-genome sequence of G. lucidum. As a result,8 regulatory factors were screened out including the transcription initiation TFIIB,the alpha/beta hydrolase super family,ALDH-SF superfamily,60 S ribosomal protein L21,ATP synthase β-subunit,microtubule associated protein Cript,prote asome subunit β-1,and transaldolase. Until now,the regulation effect of these 8 regulatory factors in G.lucidum has not been reported. This study provides candidate proteins for in-depth study on the expression regulation of LS.
Gene Library ; Intramolecular Transferases/metabolism* ; Reishi/genetics* ; Saccharomyces cerevisiae ; Transcription Factors/metabolism*