The molecular characterization of a cyclophilin A from Chinese mitten crab Eriocheir sinensis and the antifungal activity of its recombinant protein

Background: Cyclophilin A (CypA), a receptor for the immunosuppressive agent cyclosporin A (CsA), is a cis-trans peptidyl-prolyl isomerase (PPIase) which accelerates the cis-trans isomerization of prolyl-peptide bonds and interacts with a variety of proteins to regulate their activities. Results: The full-length cDNA of crab Eriocheir sinensis CypA ( Es CypA) was cloned by EST and RACE technique. The complete sequence of Es CypA cDNA contained a 5' untranslated region (UTR) of 50 bp, a 3’ UTR of 233 bp with a polyA tail, and an open reading frame (ORF) of 495 bp encoding a polypeptide of 164 amino acids with the predicted molecular weight of 17.36 kDa. The deduced amino acid sequence of Es CypA contained two highly conserved signature sequences of peptidyl-prolyl cis-trans isomerase and a pro-isomerase domain. The mRNA transcripts of Es CypA were detectable in all the examined tissues, including haemocytes, gill, hepatopancreas, gonad, muscle and heart, with higher expression level in hepatopancreas and gonad. No significant difference in the relative mRNA expression level of Es CypA was observed during the whole course of bacteria challenge, whereas it was up-regulated during fungi challenge. The purified recombinant protein r Es CypA exhibited a significant PPIase activity and an antifungal activity. Conclusions: All these results indicated that it was a typical CypA member and potentially involved in the innate immune responses of crab.