title: A mutation in the catalytic loop of Hsp90 specifically impairs ATPase stimulation by Aha1p, but not Hch1p.
abstract: Heat shock protein 90 (Hsp90) is a molecular chaperone that plays a central role in maintaining cellular homeostasis by facilitating activation of a large number of client proteins. ATP-dependent client activation by Hsp90 is tightly regulated by a host of co-chaperone proteins that control progression through the activation cycle. ATPase stimulation of Hsp90 by Aha1p requires a conserved RKxK motif that interacts with the catalytic loop of Hsp90. In this study, we explore the role of this RKxK motif in the biological and biochemical properties of Hch1p. We found that this motif is required for Hch1p-mediated ATPase stimulation in vitro, but mutations that block stimulation do not impair the action of Hch1p in vivo. This suggests that the biological function of Hch1p is not directly linked to ATPase stimulation. Moreover, a mutation in the catalytic loop of Hsp90 specifically impairs ATPase stimulation by Aha1p but not by Hch1p. Our work here suggests that both Hch1p and Aha1p regulate Hsp90 function through interaction with the catalytic loop but do so in different ways.
authors.affiliation: Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
authors.forename: Natalie K
authors.initials: NK
authors.lastname: Horvat
authors.affiliation: Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
authors.forename: Heather
authors.initials: H
authors.lastname: Armstrong
authors.affiliation: Department of Biochemistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
authors.forename: Brian L
authors.initials: BL
authors.lastname: Lee
authors.affiliation: Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Mercier
authors.affiliation: Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
authors.forename: Annemarie
authors.initials: A
authors.lastname: Wolmarans
authors.affiliation: Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
authors.forename: Jacob
authors.initials: J
authors.lastname: Knowles
authors.affiliation: Department of Biochemistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
authors.forename: Leo
authors.initials: L
authors.lastname: Spyracopoulos
authors.affiliation: Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7. Electronic address: paul.lapointe@ualberta.ca.
authors.forename: Paul
authors.initials: P
authors.lastname: LaPointe
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D020816:Amino Acid Motifs; D020134:Catalytic Domain; D018833:Chaperonins / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism*; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C475092:AHA1 protein, S cerevisiae; C117748:HCH1 protein, S cerevisiae; C074510:HSP82 protein, S cerevisiae; D018841:HSP90 Heat-Shock Proteins; D018832:Molecular Chaperones; D050505:Mutant Proteins; D029701:Saccharomyces cerevisiae Proteins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D018833:Chaperonins
keywords: Sti1p; chaperone; co-chaperone; enzyme; yeast