Cloning and characterization of Giardia intestinalis cyclophilin

Abstract

The cyclophilins (Cyps) are family members of proteins that exhibit peptidyl-prolyl cis-trans isomerase (PPIase, EC 5.2.1.8) activity and bind the immunosuppressiveagent cyclosprin A (CsA) in varying degrees. During the process of random sequencing of acDNA library made from Giardia intestinalis WB strain, the cyclophilin gene ( gicyp1 ) wasisolated. An open reading frame of gicyp1 gene was 576 nucleotides, which correspondedto a translation product of 176 amino acids (Gicyp1). The identity with other Cyps wasabout 58-71%. The 13 residues that constituted the CsA binding site of human cyclophilinwere also detected in the amino acid sequence of Gicyp1, including tryptophan residueessential for the drug binding. The single copy of the gicyp1 gene was detected in the G.intestinalis chromosome by southern hybridization analysis. Recombinant Gicyp1 proteinclearly accelerated the rate of cis trans isomerization of the peptide substrate and thecatalysis was completely inhibited by the addition of 0.5 M CsA.