Objective: To clone, express and purify the light chain(LC) of BoNT/A. Methods: A 1 364-bp gene fragment of BoNT/A LC was
amplified from Clostridium botulinum type A by PCR and inserted into pET21a vector to construct a recombinant prokaryotic expression vector pET21a-ALC. Then it was transformed into E.coli BL21 (DE3) pLysS competent cells to express recombinant BoNT/A LC induced by IPTG. The
antigenicity of recombinant BoNT/A LC was identified by Western blot. Results: BoNT/A LC gene was correctly amplified and inserted into the vectors as confirmed by sequencing and restriction analysis. The genetically engineered strain of E.coli BL21/pET21a-ALC was induced by 0.7 mmol/L IPTG for 6 h at 37℃ and a high level of expression was obtained. The target protein amounted to 23% of total cell protein and existed in inclusion body form. The recombinant BoNT/A LC protein was one-step purified by affinity chromatography with immobilized nickel-chelating NTA(Ni-NTA)and its purity was up to 97%. The good antigenicity was identified by Western blot. Conclusion: It is the first time to clone, express and purify BoNT/A LC successfully in domestic laboratories. The purified recombinant BoNT/A LC protein shows a good antigenicity. It lays foundation for preparing the antibody against BoNT/A LC and establishing a rapid detection method for BoNT/A.