Objective To clone the catalytic domain gene sequence of RgpAcd of Porphyromonas gingivalis（P.gingivalis） and to induce its fusion expression in E. coli. Methods The desired DNA fragment RgpAcd was obtained by PCR and was separately sequenced and identified by inserting into inter-vector pMD18-T vector. The correctly fragment was linked with and cloned into a prokaryotic expression vector pET-15b. The recombinant expression plasmid which had been confirmed by enzymes digestion was transformed to E. coli competent cells BL21（DE3） and expression of fusion protein was induced by IPTG. Results A 1 476 bp specific fragment was obtained and DNA sequencing showed that the fragment was consistent with those of the published. After induction with IPTG, a fusion protein of 5×104 was visualized on SDS-PAGE gel. Conclusion The protein of RgpAcd will be obtained for further study and its protein was correctly expressed in E. coli BL21 cells.
