title: Heat shock protein 90's mechanochemical cycle is dominated by thermal fluctuations.
abstract: The molecular chaperone and heat shock protein 90 (Hsp90) exists mainly as a homodimer in the cytoplasm. Each monomer has an ATPase in its N-terminal domain and undergoes large conformational changes during Hsp90's mechanochemical cycle. The three-color single-molecule assay and data analysis presented in the following allows one to observe at the same time nucleotide binding and the conformational changes in Hsp90. Surprisingly, and completely unlike the prior investigated systems, nucleotides can bind to the N-terminally open and closed state without strictly forcing the protein into a specific conformation. Both the transitions between the conformational states and the nucleotide binding/unbinding are mainly thermally driven. Furthermore, the two ATP binding sites show negative cooperativity; i.e., nucleotides do not bind independently to the two monomers. We thus reveal a picture of how nucleotide binding and conformational changes are connected in the molecular chaperone Hsp90, which has far-ranging consequences for its function and is distinct from previously investigated motor proteins.
authors.affiliation: Physik-Department (E22), Institute of Medical Engineering (IMETUM), Center for NanoScience (CeNS), Center for Integrated Protein Science (CIPSM), Technische Universität München, 85748 Garching, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Ratzke
authors.forename: Felix
authors.initials: F
authors.lastname: Berkemeier
authors.forename: Thorsten
authors.initials: T
authors.lastname: Hugel
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D018360:Crystallography, X-Ray; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D013696:Temperature
chemical_list: D029721:Drosophila Proteins; D006360:Heat-Shock Proteins; C089272:Hsp83 protein, Drosophila; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate