Objective To clone the fimA gene of Porphyromonas gingivalis（P.gingivalis） and detect its expression in Escherichia coli（E.coli）. Methods The fimA gene was obtained by PCR from the genome of P.gingivalis to construct a prokaryotic expression plasmid pT -BAD/fimA. pT -BAD/fimA was transformed into E.coli BL21（DE3） competent cells and the recombination protein was characterized by means of matrix assisted laser desorption ionisation time-offlight mass spectrometry（MALDI-TOF-MS） analysis. The bound protein was eluted with different concentrations of imidazole（250, 200, 150, 100, 50 μmol·L-1） respectively. Results DNA sequencing showed that the fragment was 99.9% consistent with that of the published. After induction with L-arabinose, a new 3.8×104 protein appeared on SDS-PAGE gel. The protein was further identified by MALDI-TOF-MS. Purity of 95% of the target protein was purified by Ni-NTA Purification System after eluted with 100 μmol·L-1 imidazole. Conclusion The fimA gene of P. gingivalis was cloned successfully and its protein was expressed correctly in E.coli. A high purity of protein FimA was obtained and it could be applied for follow-up researches.
