title: Nucleotide-dependent interaction of Saccharomyces cerevisiae Hsp90 with the cochaperone proteins Sti1, Cpr6, and Sba1.
abstract: The ATP-dependent molecular chaperone Hsp90 and partner cochaperone proteins are required for the folding and activity of diverse cellular client proteins, including steroid hormone receptors and multiple oncogenic kinases. Hsp90 undergoes nucleotide-dependent conformational changes, but little is known about how these changes are coupled to client protein activation. In order to clarify how nucleotides affect Hsp90 interactions with cochaperone proteins, we monitored assembly of wild-type and mutant Hsp90 with Sti1, Sba1, and Cpr6 in Saccharomyces cerevisiae cell extracts. Wild-type Hsp90 bound Sti1 in a nucleotide-independent manner, while Sba1 and Cpr6 specifically and independently interacted with Hsp90 in the presence of the nonhydrolyzable analog of ATP, AMP-PNP. Alterations in Hsp90 residues that contribute to ATP binding or hydrolysis prevented or altered Sba1 and Cpr6 interaction; additional alterations affected the specificity of Cpr6 interaction. Some mutant forms of Hsp90 also displayed reduced Sti1 interaction in the presence of a nucleotide. These studies indicate that cycling of Hsp90 between the nucleotide-free, open conformation and the ATP-bound, closed conformation is influenced by residues both within and outside the N-terminal ATPase domain and that these conformational changes have dramatic effects on interaction with cochaperone proteins.
authors.affiliation: Department of Microbiology, Molecular Biology and Biochemistry and Center for Reproductive Biology, University of Idaho, Moscow, ID 83844-3052, USA. jilljohn@uidaho.edu
authors.forename: Jill L
authors.initials: JL
authors.lastname: Johnson
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Halas
authors.forename: Gary
authors.initials: G
authors.lastname: Flom
mesh_terms: D000266:Adenylyl Imidodiphosphate / Q000378:metabolism*; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000378:metabolism*; D019281:Dimerization; D005656:Fungal Proteins / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D000097322:Peptidyl-Prolyl Isomerase D
chemical_list: D000266:Adenylyl Imidodiphosphate; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins; D005656:Fungal Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; C000631444:CPR6 protein, S cerevisiae; D000097322:Peptidyl-Prolyl Isomerase D; C074510:HSP82 protein, S cerevisiae; C113025:SBA1 protein, S cerevisiae; C542289:STI1 protein, S cerevisiae