title: Human cyclophilin B: a second cyclophilin gene encodes a peptidyl-prolyl isomerase with a signal sequence.
abstract: We report the cloning and characterization of a cDNA encoding a second human cyclosporin A-binding protein (hCyPB). Homology analyses reveal that hCyPB is a member of the cyclophilin B (CyPB) family, which includes yeast CyPB, Drosophila nina A, and rat cyclophilin-like protein. This family is distinguished from the cyclophilin A (CyPA) family by the presence of endoplasmic reticulum (ER)-directed signal sequences. hCyPB has a hydrophobic leader sequence not found in hCyPA, and its first 25 amino acids are removed upon expression in Escherichia coli. Moreover, we show that hCyPB is a peptidyl-prolyl cis-trans isomerase which can be inhibited by cyclosporin A. These observations suggest that other members of the CyPB family will have similar enzymatic properties. Sequence comparisons of the CyPB proteins show a central, 165-amino acid peptidyl-prolyl isomerase and cyclosporin A-binding domain, flanked by variable N-terminal and C-terminal domains. These two variable regions may impart compartmental specificity and regulation to this family of cyclophilin proteins containing the conserved core domain. Northern blot analyses show that hCyPB mRNA is expressed in the Jurkat T-cell line, consistent with its possible target role in cyclosporin A-mediated immunosuppression.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
authors.forename: E R
authors.initials: ER
authors.lastname: Price
authors.forename: L D
authors.initials: LD
authors.lastname: Zydowsky
authors.forename: M J
authors.initials: MJ
authors.lastname: Jin
authors.forename: C H
authors.initials: CH
authors.lastname: Baker
authors.forename: F D
authors.initials: FD
authors.lastname: McKeon
authors.forename: C T
authors.initials: CT
authors.lastname: Walsh
mesh_terms: D000591:Amino Acid Isomerases / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D003001:Cloning, Molecular; D004730:Endothelium, Vascular / Q000201:enzymology; D004926:Escherichia coli / Q000235:genetics; D015723:Gene Library; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D015345:Oligonucleotide Probes; D019696:Peptidylprolyl Isomerase; D016133:Polymerase Chain Reaction; D021382:Protein Sorting Signals / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
chemical_list: D002352:Carrier Proteins; D015345:Oligonucleotide Probes; D021382:Protein Sorting Signals; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase