title: Regulation of heat shock protein 90 ATPase activity by sequences in the carboxyl terminus.
abstract: Hsp90, in addition to being an abundant and pivotal cytoplasmic chaperone protein, has been shown to be a weak ATPase. In an effort to characterize the ATPase activity of hsp90, we have observed marked differences in activities among various species of hsp90. Chicken or human hsp90 hydrolyzed ATP with a k(cat) of 0.02 min(-1) and a K(m) greater than 300 microm. In contrast, yeast hsp90 and TRAP1, an hsp90 homologue found in mitochondria, were 10-100-fold more active as ATPases. Sedimentation studies confirmed that all are dimeric proteins. Chicken hsp90 mutants were then analyzed to identify regions within the protein that influence ATPase activity. A truncation mutant of chicken hsp90, N1-573, was found to be monomeric, and yet the catalytic efficiency (k(cat)/K(m)) was greater than 100 times that of the full-length protein (k(cat) of 0.24 min(-1) and K(m) of 60 microm). In contrast, an internal deletion mutant, Delta661-677, was also monomeric but failed to hydrolyze ATP. Finally, deletion of the last 30 amino acids resulted in a dimeric protein with an ATPase activity very similar to full-length hsp90. These data indicate that sequences within the last one-fourth of hsp90 regulate ATP hydrolysis.
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic Graduate School, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: Barbara A L
authors.initials: BA
authors.lastname: Owen
authors.forename: William P
authors.initials: WP
authors.lastname: Sullivan
authors.forename: Sara J
authors.initials: SJ
authors.lastname: Felts
authors.forename: David O
authors.initials: DO
authors.lastname: Toft
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002645:Chickens; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013917:Thrombin / Q000378:metabolism
chemical_list: D018841:HSP90 Heat-Shock Proteins; C092306:TRAP1 protein, human; D000255:Adenosine Triphosphate; D013917:Thrombin; D000251:Adenosine Triphosphatases