CHARACTERIZATION OF A SCHISTOSOMA-MANSONI CDNA-ENCODING A B-LIKE CYCLOPHILIN AND ITS EXPRESSION IN ESCHERICHIA-COLI

A cDNA encoding a Schistosoma mansoni cyclophilin (SmCyP) has been clo ned by polymerase chain reaction amplification using degenerate oligon ucleotides based on known conserved cyclophilin (CyP) sequences and by screening an expression cDNA library. The cDNA sequence encodes a 21. 5-kDa protein, which shares 59% sequence identity with human CyP B. Th e SmCyP protein was expressed in Escherichia coli with a hexahistidine affinity tag at its amino terminus and antibodies to the purified (Hi s(6))-SmCyP fusion protein were raised in a rabbit. Fractionation of p arasite material followed by immunoblot analysis revealed that schisto some CyP is a soluble protein. The N-terminus of the predicted protein contains a hydrophobic region, suggestive of a signal sequence. Accor dingly, a recombinant SmCyP protein, lacking the first 23 amino acids was found to share the same gel electrophoretic mobility as the parasi te-derived CyP protein, suggesting cleavage of a leader sequence. Hybr idization of genomic DNA to a full-length cDNA probe indicates that th e SmCyP gene is present as a single copy. Immunohistological experimen ts in conjunction with confocal scanning laser microscopy and immune e lectron microscopy show that SmCyP is present in abundance in the adul t worm as well as in the schistosomula. The function of CyP in the sch istosome is presently unclear, but since its ligand, cyclosporin A, ha s antischistosomal activity, its function is expected to be a vital on e.