title: Isolation, cDNA sequences, and biochemical characterization of the major cyclosporin-binding proteins of Toxoplasma gondii.
abstract: The activities of the immunosuppressive, antifungal compounds cyclosporin A (CsA), FK-506, and rapamycin are dependent upon high affinity binding proteins collectively termed immunophilins. We report the isolation, biochemical characterization, and amino acid sequences of two major CsA-binding proteins, cyclophilins, from the pathogenic protozoan, Toxoplasma gondii. The 18.5- and 20-kDa molecular mass proteins exhibit peptidylproline cis-trans-isomerase activity, which is inhibitable by 10(-8) M CsA. The amino acid sequences of these two proteins, deduced from cDNA clones, reveal up to 70% amino acid identity to previously isolated cyclophilins. The 18.5-kDa protein appears to be synthesized as a precursor with a 15 amino acid signal peptide. The amino-terminal region of the mature 20-kDa protein has significant homology to the B subunit of the calmodulin-dependent phosphatase, calcineurin. The two T. gondii cyclophilins are products of different genes and appear to have different subcellular distributions.
authors.affiliation: Department of Medicine, Yale University School of Medicine, New Haven, Connecticut 06510.
authors.forename: K P
authors.initials: KP
authors.lastname: High
authors.forename: K A
authors.initials: KA
authors.lastname: Joiner
authors.forename: R E
authors.initials: RE
authors.lastname: Handschumacher
mesh_terms: D000591:Amino Acid Isomerases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019703:Calcineurin; D002148:Calmodulin-Binding Proteins / Q000737:chemistry; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002451:Cell Compartmentation; D003524:Cyclosporins / Q000378:metabolism / Q000494:pharmacology; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary; D017125:Genes, Protozoan; D006801:Humans; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase; D010749:Phosphoprotein Phosphatases / Q000737:chemistry; D015800:Protozoan Proteins / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014122:Toxoplasma / Q000235:genetics / Q000276:immunology*
chemical_list: D002148:Calmodulin-Binding Proteins; D002352:Carrier Proteins; D003524:Cyclosporins; D017931:DNA Primers; D018076:DNA, Complementary; D015800:Protozoan Proteins; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase