title: Heterogeneous binding of the SH3 client protein to the DnaK molecular chaperone.
abstract: The molecular chaperone heat shock protein 70 (Hsp70) plays a vital role in cellular processes, including protein folding and assembly, and helps prevent aggregation under physiological and stress-related conditions. Although the structural changes undergone by full-length client proteins upon interaction with DnaK (i.e., Escherichia coli Hsp70) are fundamental to understand chaperone-mediated protein folding, these changes are still largely unexplored. Here, we show that multiple conformations of the SRC homology 3 domain (SH3) client protein interact with the ADP-bound form of the DnaK chaperone. Chaperone-bound SH3 is largely unstructured yet distinct from the unfolded state in the absence of DnaK. The bound client protein shares a highly flexible N terminus and multiple slowly interconverting conformations in different parts of the sequence. In all, there is significant structural and dynamical heterogeneity in the DnaK-bound client protein, revealing that proteins may undergo some conformational sampling while chaperone-bound. This result is important because it shows that the surface of the Hsp70 chaperone provides an aggregation-free environment able to support part of the search for the native state.
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Jung Ho
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Dongyu
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Christopher
authors.initials: C
authors.lastname: Hughes
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Okuno
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Ashok
authors.initials: A
authors.lastname: Sekhar
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706 cavagnero@chem.wisc.edu.
authors.forename: Silvia
authors.initials: S
authors.lastname: Cavagnero
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism; D004331:Drosophila melanogaster; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D012997:Solvents; D013379:Substrate Specificity; D018909:src Homology Domains
chemical_list: D029721:Drosophila Proteins; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; D012997:Solvents; C080530:drk protein, Drosophila; D000244:Adenosine Diphosphate; C063842:dnaK protein, E coli
keywords: DnaK; Hsp70; molecular chaperone; protein folding; triple-resonance NMR