Production of antimicrobial peptide (Oxysterlin 1) in Escherichia coli with ELP self-cleavage tag / 生物工程学报

Antimicrobial peptides are the most promising alternatives to antibiotics. However, the strategy of producing antimicrobial peptides by recombinant technology is complicated and expensive, which is not conducive to the large-scale production. Oxysterlin 1 is a novel type of cecropin antimicrobial peptide mainly targeting on Gram-negative bacteria and is of low cytotoxicity. In this study, a simple and cost-effective method was developed to produce Oxysterlin 1 in Escherichia coli. The Oxysterlin 1 gene was cloned into a plasmid containing elastin-like polypeptide (ELP) and protein splicing elements (intein) to construct the recombinant expression plasmid (pET-ELP-I-Oxysterlin 1). The recombinant protein was mainly expressed in soluble form in E. coli, and then the target peptide can be purified with a simple salting out method followed by pH changing. The final yield of Oxysterlin 1 was about 1.2 mg/L, and the subsequent antimicrobial experiment showed the expected antimicrobial activity. This study holds promise for large-scale production of antimicrobial peptides and the in-depth study of its antimicrobial mechanism.

Expression and purification of soluble recombinant antibody fragment and immunotoxin in Escherichia coli using Npu DnaE C-cleavage mutant / 中国药科大学学报

@#The purpose of this experiment is to achieve the soluble expression of immunotoxins in Escherichia coli and avoid the complicated operation caused by the formation of inclusion bodies. An anti-mesothelin monoclonal antibody SS1 and it′s derivative SS1P which composing of SS1 and a truncated pseudomonas exotoxin PE38KDEL were used as the passenger protein. We took advantages of solubility promoting fusion tags and the self-cleaving split intein in recombinant antibody fragment and immunotoxin expression and purification. We constructed solubilizing tags-NpuCD118G fusion tags, and recombinant SS1/SS1P were fused at the C-terminal of the fusion tags. The constructs were expressed in E. coli(SHuffle T7)cytoplasm in soluble form at low temperature. Dextrin Beads 6FF column and Nickel column was used to purify the fusion protein. The self-cleavage of the fusion protein was achieved by adding the NpuN fragment. The released solubilizing tag and unreacted precursor were removed by Nickel column and the cleaved antibody fragment and immunotoxinwere further captured by Capto L. The dissociation constant of the obtained Fv and immunotoxin were determined by Fortebio. In summary, the current method could enhance the solubility of antibody fragment and immunotoxin in E. coli, and could improve the purification process. This method provides a reference for the development of a method for soluble expression and purification of immunotoxin-type pharmaceutical recombinant proteins based on the Escherichia coli expression system.

Splicing reaction of split inteins between non-natural exteins containing amino acid sequences of antibody hinge area / 中国药科大学学报

@#Intein is a functional protein that mediates self-cleavage from precursor protein and simultaneously connects the exteins on both sides of the intein via peptide bonds. Among all kinds of inteins, split intein has a wide range of applications in the field of antibody ligation. However, since the naturally split intein specifically recognizes the first three amino acid sequences “cysteine, phenylalanine, and asparagine”(CFN)of the extein, exogenous amino acids are inevitably introduced after the protein splicing reaction. In this study, the amino acid sequence “cysteine, aspartic acid, and lysine”(CDK)of the antibody hinge region was substituted for “CFN” as the recognition site for the intein and the split intein Npu DnaE was mutated into Npu*GEP DnaE. The results showed that the mutant could recognize “CDK” and the intein splicing reaction could successfully take place. The factors affecting the intein splicing reaction platform, such as pH, temperature and the concentration of NaCl and DTT were investigated in this study. The results showed that the splicing reaction of the mutant performed well, which indicated its potential usefulness in bispecific antibody assembly. In conclusion, the problem of introducing foreign amino acids was alleviated, the broadness of intein substrate was further expanded, and further technical support for the application of intein to the antibody assembly was provided.

Expression and polyclonal antibody preparation of the tegument protein UL48 encoded by MDV / 中国兽医学报

UL48 plays essential role in replication of MDV genome and interacts with UL36 as well as other MDV tegument proteins.To investigate the interaction between UL48 and UL36 during MDV oncogenisis,antibody against UL48 was prepared and characterized in current study.UL48 gene was amplified from MDV-Ⅰ genome and then subcloned into pTYB1 and pGEX-4T3 vectors for UL48 expression with induction of IPTG in BL21(DE3) E..coli cells.Chitin-sepharose and Glutathion-sepharose were,respectively,used to purify fusion protein intein-UL48 and GST-UL48.Four subcutaneous injections of intein-UL48 fusion protein were done on the lower back and the thigh of rabbit and then other three injections with an interval 10 days.The titer of antibody was measured by the sandwich ELISA with UL48 protein isolated from GST-UL48 after cleavage of thrombin.Western blot was carried out for specificity analysis of antibody against UL48 protein.The results suggested that UL48 antibody was succesfully prepared,and its titer was 1 ∶ 512 000.

Construction of spider silk functional platform via intein trans-splicing / 生物工程学报

To provide technical support for spider silk functional modification, we developed a simple and efficient functional platform via intein trans-splicing. Small ubiquitin-related modifier protein (SUMO) was fused to the recombinant spider silk protein (W2CT) by peptide bond via S0 split intein Ssp DnaB trans-splicing, resulting in a protein SUMOW2CT. However, incorporation of exogenous protein led to mechanical property defect and lower fiber yield, and also slowed down the fiber assembly velocity but no obvious differences in supercontraction and chemical resistance when compared with fibers from W2CT (W). SUMO protease digestion showed positive results on the fibers, indicating that the SUMO protein kept its native conformation and bioactive. Above all, this work provides a technical support for spider silk high simply and efficient functionalized modification.

Advances in protein cyclization / 生物工程学报

Proteins, which exist mainly in linear form in vivo, are easily affected by the change of ambient temperature and pH. The application of proteins (enzymes) in the fields of industrial catalyzing, food manufacturing and medicine are restricted due to their properties. The cyclic structure of natural cyclic peptides confers high thermal stability on itself; such mechanism can be referred to in further enhancement of the thermal stability and transformation of the structure of enzymes. This article reviewed the latest progress in the domestic and international studies on protein cyclization and summarized the traditional methods (such as protein trans-splicing, expressed protein ligation and sortase-catalyzed transpeptidation) in protein cyclization. A novel method based on SpyTag/SpyCather-mediated enzyme cyclization was discussed in more detail.

Intein-mediated expression of cecropin in escherichia coli

Different strategies have been used to overcome the difficulties to produce antimicrobial peptides. Here we used Intein Mediated Purification with an Affinity Chitin-binding Tag (IMPACT-System, New England Biolabs) for the expression of the antimicrobial peptide cecropin to reduce its sensitivity to intracellular proteases and use its inducible self-cleaving capability to remove the carrier. Cecropin was cloned into suitable expression vector pTYB11, and expression induced by IPTG in Escherichia coli ER2566. The use of 22ºC induction allowed the expression of cecropin with its intein carrier in soluble form. Cell extracts were purified by chitin affinity chromatography and intein-mediated splicing of the target protein was achieved by thiol addition, obtaining a final yield of 2.5 mg cecropin/l. Cecropin cleaved from the intein had its proper biologically active form, showing a micromolar antimicrobial activity against Vibrio ordalii, Vibrio alginolyticus and Escherichia coli.

Inteins in pathogenic fungi: a phylogenetic tool and perspectives for therapeutic applications

Inteins or "internal proteins" are coding sequences that are transcribed and translated with flanking sequences (exteins). After translation, the inteins are excised by an autocatalytic process and the host protein assumes its normal conformation and develops its expected function. These parasitic genetic elements have been found in important, conserved proteins in all three domains of life. Most of the eukaryotic inteins are present in the fungi kingdom and the PRP8 intein is one of the most widespread inteins, occurring in important pathogens such as Cryptococcus neoformans (varieties grubii and neoformans), Cryptococcus gattii, Histoplasma capsulatum and Paracoccidioides brasiliensis. The knowledge of conserved and non-conserved domains in inteins have opened up new opportunities for the study of population variability in pathogenic fungi, including their phylogenetic relationships and recognition or diagnoses of species. Furthermore, inteins in pathogenic fungi should also be considered a promising therapeutic drug target, since once the autocatalytic splicing is inhibited, the host protein, which is typically vital, will not be able to perform its normal function and the fungal cell will not survive or reproduce.

Current Strategies for Polypeptide Fusion Tags Removal / 生物化学与生物物理进展

Using gene fusion technology, polypeptide fusion tags can be engineered into target proteins at the genetic level.The resultant recombinant proteins may possess the biochemical properties of the imported fusion tags.Therefore, it is possible to take advantage of fusion tags to improve and evaluate protein expression, to detect and track protein targets, and to purify and characterize proteins.However, it is necessary to eliminate any influence of the fusion tag in structural characterization experiments or in isolating pharmaceutical proteins.Scientists must therefore remove fusion tags prior to structural and functional analyses when fusion tags are suspected of interfering with the biological activity of a protein or influencing its behavior.The fusion tag can be removed by several methods including harsh chemical treatment, mild enzymatic cleavage by endoprotease or exoprotease, and intein-mediated self-cleavage.Here the literature is reviewed in relation to principles, applications, and approaches of each method.

Large Protein Production Through Split Intein-Mediated Trans-Splicing / 中国生物工程杂志

Npu DnaE intein was used to produce some large proteins,which were difficult to obtain through conventional expression systems.A T7 expression system was described,by which the gene of T7 RNA polymerase is split into two pieces,and each piece fuses with Npu DnaE N-and C-terminal sequences respectively.Functional T7 RNA polymerase is created by mixing the two kinds of fusion constructs in vitro.The approach of split intein-mediated production of large proteins,in theory,readily generalizable to the purification of other large,cytotoxic or membrane proteins.

Preparation and Identification of Recombinant Vasoactive Intestinal Peptide / 中国生物工程杂志

In order to prepare the recombinant vasoactive intestinal peptide (VIP) using intein mediated rapid purification system,the cDNA encoding the recombinant VIP was designed and synthesized according to the preference of E.coli,and then was cloned into the expression vector PTWIN. The recombinant plasmid PTWIN-VIP was transformed into expression host E.coli strain ER2566.The fusion protein consisting of the recombinant VIP,intein and chitin binding domain was expressed and purified by chitin affinity chromatography. The target peptide was released from the fusion protein by changing the temperature and the pH of the cleavage buffer. The molecular weight of the recombinant VIP was determined by the mass spectrometry and the results was conformity with the theoretical value. The preliminary bioactivity assay indicated that the recombinant VIP decreased the serum resistin levels significantly in LPS-induced acute inflammation. The preparation and the characterization of anti-inflammatory effects of the recombinant VIP layed the foundation for its further application.

Recent Advance in the Study of Intein / 生物化学与生物物理进展

Since the first intein was found, more and more attenti on were paid on it. It not only enrichs the content of the process that the gene transfers its information but also can be used in protein purification. The rec ent advance in the sequence characteristic, transfer, evolution and the mechanis m of splicing of intein was summarized.