ABSTRACT
Objective To construct the prokaryontic expression vector of the gene fragment which encodes the transpeptidase domain of penicillin binding protein 2a(PBP2a) of methicillin‐resistant Staphylococcus aureus(MRSA) ,and to express ,purify and i‐dentify the objective protein .Methods Strains of MRSA were isolated and identified from clinical samples ,according to the se‐quence of mecA gene recorded in GenBank ,the primers of mecA fragment which encoded the transpeptidase domain of PBP2a was designed .The gene fragment from MRSA was amplified by using polymerase chain reaction(PCR) and cloned into pET28a(+ ) plasmid .After being identified by enzyme digestion and sequencing ,the recombinant plasmid was transformed into the strain of Escherichia coli BL21(DE3)plysS .The expression of transpeptidase domain of PBP2a was induced by 0 .7 mmol/L IPTG ,the ex‐pressed products were purified by using Ni afinity chromatography ,then were analyzed by using Western blot .Results The recom‐binant expression vector was digested by BamHⅠ and EcoRⅠ ,and the products were at the expected size .The result of sequencing showed two bases undergoing mutation ,while there were no frameshift mutations .The expressed protein was identified by using SDS‐PAGE and Western blot ,a new protein band was visible at the relative molecular mass of 38 × 103 .Conclusion The corre‐sponding prokaryotic expression vector is successfully constructed ,and the transpeptidase domain of PBP2a is successfully ex‐pressed and purified .