Objective To prepare recombinant plasminogen activator(Pla) protein in E.coli BL21 cells that can be used in studying interactions between Yersinia pestis proteins and immunologic diagnosis of plague.Methods The pla gene was amplified by PCR and cloned into the pET28a expression vector.E.coli BL21 competent cells were transformed with the recombinant vectors, and isopropyl-β-D-thiogalactopyranoside ( IPTG) was added to induce expression of Pla protein. The expressed protein was detected by SDS-PAGE electrophoresis.The inclusion bodies of Pla protein were denatured in 8 mol/L urea, and then refolded using gradient urea solutions.The purified protein was identified by SDS-PAGE electrophoresis and Western blot.Results and Conclusion The constructed expression vector was demonstrated to be correct through agarose gel electrophoresis and sequencing.The recombinant Pla protein was accumulated as an inclusion body in E.coli, and the overexpression product was mainly a target protein, the yield of which was very high.SDS-PAGE purity of the bioactive Pla protein was obtained by denaturing and refolding the inclusion bodies.This study provides a simple and quick method for highly efficient preparation of biologically active Pla protein.

Objective To establish a simple and quick loop-mediated isothermal amplification (LAMP)method for detection of Yersinia pestis.Methods LAMP Primers were designed based on the specific sequence 3a in Y.pestis chromosome.LAMP reaction results were detected using turbidity meter or visual method.The specificity of the constructed method was evaluated by detecting Y.pestis and its closely-related bacteria.The different dilution DNA template was detected with LAMP and PCR to evaluate the sensitivity of the method.Results Thirty strains of bacteria closely related to Y.pestis were detected by the constructed LAMP,and all the results were negative,indicating that the method had a very high specificity.The detection sensitivity of this LAMP assay was 20 pg of DNA per reaction,which was ten-fold that of the regular PCR.The detection reaction was completed in 25 min.Conclusion This LAMP method is quick,sensitive, specific and simple,which is expecked to become an effective method for rapid detection of Y.pestis on the scene.