title: Functional analysis of the yeast 40 kDa cyclophilin Cyp40 and its role for viability and steroid receptor regulation.
abstract: We have identified and characterized a homolog of the 40 kDa cyclophilins in the budding yeast Saccharomyces cerevisiae. At the amino acid level, this novel yeast cyclophilin, termed Cyp40, is 47% identical to human cyclophilin-40. Recombinant Cyp40 produced in bacteria has a peptidyl-prolyl cis-trans isomerase activity with a catalytic efficiency (k[cat]/K[m]) of 0.5 x 10(6)M(-1)s(-1), which can be inhibited by cyclosporin A with an IC50 value of 60nM. Using a polyclonal antibody against Cyp40 we have found that Cyp40 is predominantly cytoplasmic, and that its expression is induced 3-4-fold by heat shock. Moreover, Cyp40 can be coprecipitated from yeast extracts with the cytosolic molecular chaperone Hsp90. Surprisingly, a Cyp40-deficient yeast strain is fully viable at normal and elevated temperatures. Cyp40 is also dispensable for normal regulation of vertebrate steroid receptors in yeast. While other immunophilins could conceivably compensate a Cyp40 defect, our results are compatible with the notion that immunophilins may be fortuitous partners in the biochemically established steroid receptor-Hsp90 complex.
authors.affiliation: Département de Biologie Cellulaire, Université de Genève, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Warth
authors.forename: P A
authors.initials: PA
authors.lastname: Briand
authors.forename: D
authors.initials: D
authors.lastname: Picard
mesh_terms: D000591:Amino Acid Isomerases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D016572:Cyclosporine / Q000494:pharmacology; D003593:Cytoplasm / Q000201:enzymology; D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D005656:Fungal Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D019696:Peptidylprolyl Isomerase; D011987:Receptors, Steroid / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D013237:Stereoisomerism; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; C074510:HSP82 protein, S cerevisiae; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D007166:Immunosuppressive Agents; D011987:Receptors, Steroid; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D016572:Cyclosporine; D004706:Endodeoxyribonucleases; D001616:beta-Galactosidase; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase