title: S-cyclophilin. New member of the cyclophilin family associated with the secretory pathway.
abstract: Cyclophilin is an abundant and ubiquitous cytosolic protein that is conserved throughout evolution from man to bacteria. It is the target of the immunosuppressive drug cyclosporin A. Cyclophilin has peptidyl-prolyl cis/trans-isomerase activity, and it accelerates protein folding in vitro, suggesting that it might be involved in the folding of cytosolic proteins. We describe a novel cyclophilin-like protein, S-cyclophilin, in the chick. Analysis of S-cyclophilin cDNA revealed the presence of a signal sequence followed by an open reading frame coding for a protein very similar to cytosolic cyclophilin, except for the presence of unique additional short amino acid segments at the N and C termini of the protein. S-Cyclophilin mRNA was abundant and present in all embryonic chick tissues tested. Cyclophilin and S-cyclophilin are coded by separate genes in the chick genome. Recombinant S-cyclophilin was expressed in insect cells by means of the baculovirus system. Pulse-chase experiments revealed that a significant fraction of newly synthesized recombinant S-cyclophilin was rapidly secreted into the culture medium. Our findings indicate that cyclophilins are associated with most if not all intra- and extracellular compartments and suggest that enzyme-assisted conformational conversions in proteins might also take place in post-endoplasmic reticulum compartments, possibly including the extracellular space.
authors.affiliation: Friedrich Miescher Institute, Basel, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Caroni
authors.forename: A
authors.initials: A
authors.lastname: Rothenfluh
authors.forename: E
authors.initials: E
authors.lastname: McGlynn
authors.forename: C
authors.initials: C
authors.lastname: Schneider
mesh_terms: D000591:Amino Acid Isomerases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002642:Chick Embryo; D003001:Cloning, Molecular; D003524:Cyclosporins / Q000378:metabolism; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D015723:Gene Library; D007313:Insecta; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D019696:Peptidylprolyl Isomerase; D021382:Protein Sorting Signals / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D013116:Spinal Cord / Q000502:physiology; D014162:Transfection
chemical_list: D002352:Carrier Proteins; D003524:Cyclosporins; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D004247:DNA; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase