[Cloning and expression of L-like cysteine protease of Anisakis simplex].

Objective: To clone and express the full lenth of L-like cysteine protease gene of Anisakis simplex (AsCP).

Methods: According to L-like cysteine protease encoding gene of A. simplex from GenBank EST database, specific primers were designed to amplify 3'-end of AsCP gene using rapid-amplification of cDNA ends (RACE), and the full lenth of the L-like cysteine protease gene was obtained. Specific primers were designed according to the full length of the gene. Using total RNA of A. simplex third-stage larvae, coding sequence of the AsCP gene was amplified by RT-PCR. The PCR product was digested by EcoR I and Sal I, and cloned into pET32a(+) vector. The recombinant plasmid was checked by double enzyme digestion and sequencing, and the positive recombinant plasmid was transformed into Escherichia coli BL21 (DE3). Expression of the protein induced by IPTG of gradient concentration (0.2, 0.2, 0.4, 0.6, 0.8, 1.0, and 1.2 mmol/L) and by the same concentration (1 mmol/L) of IPTG at different time(0, 1, 1.5, 2, 2.5, 3, 3.5, and 4 h) was conducted. The expression situation of recombinant protein was analyzed by SDS-PAGE.

Results: A 1211 bp of 3'-end of AsCP gene was amplified by 3'RACE, full length of the gene was 1462 bp and coding 411 amino acids. It showed 36.4% identity with the L-cysteine protease of Caenorhabditis elegans. Double enzyme digestion of the constructed recombinant plasmid pET32a(+)-AsCP showed that there was about 1150 bp fragment, the constructed recombinant plasmid was then identified by sequencing. SDS-PAGE showed that the recombinant protein (Mr 60,000) was identical with the target. IPTG showed little effect on the protein expression, and the production of protein was up to maximum after 2 hours induction.

Conclusion: The AsCP gene has been cloned and expressed.