ABSTRACT
@#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.
ABSTRACT
As internal protein elements , inteins are self-excised from their host protein and catalyze ligation of exteins with a peptide bond .They are widely found in all the three domains of the biological kingdom , and in viral proteins .Intein-mediated protein splicing is a posttranslational autocatalytic process that does not require auxiliary enzymes or cofactors . Protein splicing involves four intramolecular reactions and a small number of key catalytic residues in the intein and exteins . The development of expressed protein ligation ( EPL ) and protein trans-splicing ( PTS ) is assisted by inteins and protein splicing.This review introduces the biosynthesis of backbone-cyclized peptides libraries , and describes the applications of cyclic polypeptides and their prospective applications in the future .
ABSTRACT
During its biosynthesis in developing Canavalia brasiliensis seeds, the lectin ConBr undergoes a form of protein splicing in which the order of the N- and C-domains of the protein is reversed. To investigate whether these events can occur in other eukaryotic organisms, an expression system based on Pichia pastoris cells was established. A DNA fragment encoding prepro-ConBr was cloned into the vector pPICZB, and the recombinant plasmid was transformed in P. pastoris strain GS115. Ten clones were screened for effective recombinant protein production. Based on Western blot analysis of the two clones with the highest level of protein expression: 1) diffuse high-molecular mass immunoreactive bands were produced as early as 24 h after induction; 2) a single-, high-molecular mass protein was secreted into the medium, and 3) a significant fraction of the recombinant polypeptides that cross-reacted with anti-ConBr antibodies comprised a band of approximately 34.5 kDa. Diffuse protein bands with high molecular masses are attributed to hyperglycosylation at the single potential N-glycosylation site located in the linker peptide of prepro-ConBr. In contrast, native ConBr is made up of three polypeptides, the intact alpha chain (aa 1-237) and the fragments beta (aa 1-118) and gamma (aa 119-237), which have apparent molecular masses of 30, 16 and 12 kDa, respectively. Apparently, the yeast P. pastoris is not able to carry out all the complex post-translational proteolytic processing necessary for the biosynthesis of ConBr.