Cloning and expression of Listeria phage endolysin CBD protein

Listeria monocytogenes phage endolysin cell- wall binding domain( CBD) can specifically recognize Listeria cells.The amplified CBDP40 gene was inserted into vector p ET32a( +) and introduced into Escherichia coli expression system in order to obtain the recombinant strain. The recombinant cells were induced with IPTG and the recombinant protein was analysed for its activity.An evident induced protein band at 38 ku was observed by sodium dodecyl sulfate polyacrylamide gel electrophoresis( SDS- PAGE) after 0.1 mmol / L IPTG induction,which was in accord with the expected molecular weight. Recombinant protein CBDP40 was obtained in the supernatant after cell sonification and purified by nickel- chelating affinity chromatography with the yield of0.908 mg / m L in the elute. The results of cell binding assay and indirect ELISA showed that CBDP40 had biological activity with the function of Listeria identification. Recombinant expression,purification and activity determination of CBD may lay the foundation for further studying the physico- chemical properties and mechanism of endolysin.