Peptidylprolyl cis/trans isomerase activity and molecular evolution of vertebrate Cyclophilin A.

Peptidylprolyl isomerases (PPIase) cyclophilin A (CypA, encoded by PPIA) is a typical member of the Cyclophilin family and is involved in protein folding/translocation, signal transduction, inflammation, immune system regulation, apoptosis and virus replication. In the present study, we investigated the PPIase activity and genetic variation of vertebrate CypA. According to the GenBank reference sequences, vertebrate PPIA genes were cloned, among which the bat (Myotis davidi) and duck (Anas platyrhynchos) PPIA genes were reported for the first time. Then PPIA genes were sub-cloned into the expression vector pGEX-6p-1 and expressed in Escherichia coli. Recombinant CypA proteins were purified by using sepharose 4B affinity chromatography and the GST tag was cleaved, followed by gel filtration. The PPIase activity assay indicated that there was no significant difference in the catalytic activity of prolyl peptide bond isomerization among 12 different vertebrate CypA proteins. In addition, the genetic variation and molecular evolution analysis showed that these vertebrate CypA proteins had the same CsA binding site and the PPIase active sites. Furthermore, the predicted structure and gene localization were remarkable conserved. Our data suggested that the important residues of CypA were highly conserved, which is crucial for its PPIase activity and cellular functions.