Abstract
Major and minor isoforms of cyclophilin (CyP-18), a 17.8-kDa protein with peptidyl-prolyl cis-trans isomerase activity, comprise the primary intracellular binding proteins for cyclosporin A. Additional CyP-like proteins with approximate molecular masses of 22 (CyP-22) and 40 kDa (CyP-40) have been recovered from the soluble fraction of calf brain along with CyP-18 by adsorption onto a cyclosporin A affinity column and elution with cyclosporin A. Based on a limited number of peptide sequences from CyP-22, it appears that we have isolated from tissue CyPB, a protein whose sequence was deduced previously from cloned cDNA. The 40-kDa protein was separated from CyP-18 and CyP-22 on a molecular sieving column. Isoelectric focusing of CyP-40 yielded two bands at pI 5.3 and 5.5, in contrast to the basic pI values of CyP-18. Some tryptic peptides from CyP-40 were found to be highly homologous but not identical to bovine CyP-18; others were not significantly homologous to CyP-18 or any other protein in the data base. Unlike the major and minor isoforms of Cyp-18, monospecific polyclonal anti-CyP-18 antibodies did not cross-react with CyP-22 and CyP-40. Likewise, anti-CyP-40 serum minimally cross-reacts with CyP-18 and CyP-22. Cyp-40 possesses peptidyl-prolyl cis-trans isomerase activity which is less sensitive to inhibition by cyclosporin A (IC50 = 300 nM) than is CyP-18 (IC50 = 20 nM).
Highlights
17.8-kDa protein with peptidyl-prolyl cis-trans iso- tion of two apparently distinct but related binding proteins merase activity, comprisetheprimaryintracellular for both FK506 [12, 13] and rapamycin [14], potent binding proteins for cyclosporin A
It has been demonstrated that cyclosporin A [19, 20] and FK506 [21],when associated with the appropriate binding protein, assume altered conformations that may be responsible for their role in modulation of the immune response
In vitro studies have shown that complexes of cyclosporin A-CyP and FK506-FKBP, but not rapamycin-FKBP or any of the drugs alone, bind to and inhibit the protein phosphataseactivity of calcineurin, impli
Summary
The abbreviations used are: PPIase, peptidyl-prolyl cis-trans isomerase; SDS, sodium dodecyl sulfate; PAGE, polyacrylamide gel Materials electrophoresis; IEF, isoelectric focusing; HEPES, 4-(2-hydroxy- Cyclosporin A and 8-ornithinocyclosporin A were generous gifts ethyl)-1-piperazineethanesulfoniaccid. Hepatocytes were prepared by the Liver Research Core Center, Yale University, from male Sprague-Dawley rats, by the collagenase perfusion technique [30]A. ll chemicals unless otherwise stated were purchased from Sigma
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
