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.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of Biological Chemistry|
|State||Published - 1991|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology