title: Substrate-binding domain conformational dynamics mediate Hsp70 allostery.
abstract: Binding of ATP to the N-terminal nucleotide-binding domain (NBD) of heat shock protein 70 (Hsp70) molecular chaperones reduces the affinity of their C-terminal substrate-binding domain (SBD) for unfolded protein substrates. ATP binding to the NBD leads to docking between NBD and βSBD and releasing of the α-helical lid that covers the substrate-binding cleft in the SBD. However, these structural changes alone do not fully account for the allosteric mechanism of modulation of substrate affinity and binding kinetics. Through a multipronged study of the Escherichia coli Hsp70 DnaK, we found that changes in conformational dynamics within the βSBD play a central role in interdomain allosteric communication in the Hsp70 DnaK. ATP-mediated NBD conformational changes favor formation of NBD contacts with lynchpin sites on the βSBD and force disengagement of SBD strand β8 from strand β7, which leads to repacking of a βSBD hydrophobic cluster and disruption of the hydrophobic arch over the substrate-binding cleft. In turn, these structural rearrangements drastically enhance conformational dynamics throughout the entire βSBD and particularly around the substrate-binding site. This negative, entropically driven allostery between two functional sites of the βSBD-the NBD binding interface and the substrate-binding site-confers upon the SBD the plasticity needed to bind to a wide range of chaperone clients without compromising precise control of thermodynamics and kinetics of chaperone-client interactions.
authors.affiliation: Astbury Centre for Structural Molecular Biology and Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom; a.zhuravleva@leeds.ac.uk gierasch@biochem.umass.edu.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Zhuravleva
authors.affiliation: Department of Biochemistry and Molecular Biology and Department of Chemistry, University of Massachusetts, Amherst, MA 01003 a.zhuravleva@leeds.ac.uk gierasch@biochem.umass.edu.
authors.forename: Lila M
authors.initials: LM
authors.lastname: Gierasch
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000494:Allosteric Regulation / Q000502:physiology*; D002247:Carbon Isotopes; D003903:Deuterium; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism; D006706:Homeostasis / Q000502:physiology*; D007700:Kinetics; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009587:Nitrogen Isotopes; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D002247:Carbon Isotopes; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D009587:Nitrogen Isotopes; D000255:Adenosine Triphosphate; D003903:Deuterium; C063842:dnaK protein, E coli
keywords: NMR chemical shift perturbations; conformational selection; entropically driven allostery; molecular chaperone; protein quality control