[Cloning, expression and purification of allergen arginine kinase from Periplaneta americana and its allergic activity].

Objective: To clone the gene of arginine kinase (AK) from Periplaneta americana, produce its recombinant protein and investigate its allergenicity.

Method: The cDNA of AK was cloned using specific primers from the total RNA of P. americana. The cloned gene was inserted into pMD18-T vector and digested by BamHI and HindIII. The cDNA was sequenced and subcloned into pET-28a expression vector. The cloned AK cDNA gene was expressed in Escherichia coli BL21 (DE3) by IPTG induction. The recombinant AK (rAK) was purified by metal (Ni2+) chelating affinity chromatography. Its allergenicity was examined by both Western blotting and enzyme-linked immunosorbent assay (ELISA).

Result: The cloned cDNA ORF sequence (Accession no. EU429466) contained 1068 bp and encoded 365 amino acids. Its sequence homology with the published one (Accession no. AY563004) was 99.9% at nucleotide level. The allergen rAK was highly expressed in E. coli BL21 (DE3) as a soluble protein mainly with the molecular weight of about Mr 45000 under induction of IPTG and purified by 6-His-tag purification system. Both in the non-denaturalization and denaturalization conditions, the recombinant allergen was identified as its affinity to IgE antibodies from the cockroach-allergic patient sera by Western blotting and ELISA.

Conclusion: The recombinant cockroach arginine kinase has been obtained with proper allergenicity.