Isolation and partial characterization of membrane-associated cyclophilin and a related 22-kDa glycoprotein.
The presence of membrane-associated proteins which stereospecifically bind cyclosporin A and react with anti-cyclophilin antibodies has been documented in rat tissues. Extraction of membranes with 6 M urea or 0.5% Chaps releases cyclosporin-binding activity that is 5-12% of that found in cytosol. Cyclosporin-A-binding proteins are present in most subcellular organelles of liver, but microsomes contain the greatest activity. These proteins can be purified by adsorption onto a cyclosporin-A affinity column and elution with cyclosporin A. Two major fractions are resolved on SDS/PAGE: an 18-kDa fraction is comprised of two isoforms that are similar if not identical to the two major cytosolic isoforms of cyclophilin. In addition, in microsomes an approximately equal quantity of a 22-kDa glycoprotein was detected. Based on partial sequencing (five peptides, 89 amino acids) this protein is similar but not identical to human cyclophilin B. This 22-kDa isoform is poorly recognized by affinity-purified anti-cyclophilin antibodies and comprises several predominant isoforms (pI approximately 9.3-9.6). Selective binding of membrane 22-kDa cyclophilin to peanut lectin suggests the oligosaccharides contain a terminal galactosyl-N-galactosamine residue.
Thalhammer
T
T
Department of General and Experimental Pathology, Vienna, Austria.
Kieffer
L J
LJ
Jiang
T
T
Handschumacher
R E
RE
D000591:Amino Acid Isomerases / Q000302:isolation & purification* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002846:Chromatography, Affinity; D016572:Cyclosporine / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000302:isolation & purification* / Q000378:metabolism; D051379:Mice; D008862:Microsomes, Liver / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D019696:Peptidylprolyl Isomerase; D051381:Rats; D012689:Sequence Homology, Nucleic Acid; D013154:Spleen / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D016572:Cyclosporine; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase