title: Molecular chaperone machines: chaperone activities of the cyclophilin Cyp-40 and the steroid aporeceptor-associated protein p23.
abstract: Molecular chaperones are essential proteins that participate in the regulation of steroid receptors in eukaryotes. The steroid aporeceptor complex contains the molecular chaperones Hsp90 and Hsp70, p48, the cyclophilin Cyp-40, and the associated proteins p23 and p60. In vitro folding assays showed that Cyp-40 and p23 functioned as molecular chaperones in a manner similar to that of Hsp90 or Hsp70. Although neither Cyp-40 nor p23 could completely refold an unfolded substrate, both proteins interacted with the substrate to maintain a nonnative folding-competent intermediate. Thus, the steroid aporeceptor complexes have multiple chaperone components that maintain substrates in an intermediate folded state.
authors.affiliation: Department of Biochemistry, Molecular Biology and Cell Biology, Rice Institute for Biomedical Research, Northwestern University, 2153 North Campus Drive, Evanston, IL 60208, USA. r-morimoto@nwu.edu
authors.forename: B C
authors.initials: BC
authors.lastname: Freeman
authors.forename: D O
authors.initials: DO
authors.lastname: Toft
authors.forename: R I
authors.initials: RI
authors.lastname: Morimoto
mesh_terms: D000591:Amino Acid Isomerases / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins; D050883:HSC70 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D006358:Hot Temperature; D018832:Molecular Chaperones / Q000378:metabolism / Q000502:physiology*; D019696:Peptidylprolyl Isomerase; D010750:Phosphoproteins / Q000378:metabolism / Q000502:physiology*; D000071876:Prostaglandin-E Synthases; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D012995:Solubility; D001616:beta-Galactosidase / Q000737:chemistry
chemical_list: D002352:Carrier Proteins; D000081406:Peptidyl-Prolyl Isomerase F; D050883:HSC70 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; C000631446:PPIF protein, mouse; D010750:Phosphoproteins; C489791:Stip1 protein, mouse; D001616:beta-Galactosidase; D000591:Amino Acid Isomerases; D021983:Cyclophilins; D019696:Peptidylprolyl Isomerase; C490849:PTGES3 protein, human; D000071876:Prostaglandin-E Synthases