Conformation transitions of the polypeptide-binding pocket support an active substrate release from Hsp70s

Nat Commun. 2017 Oct 31;8(1):1201. doi: 10.1038/s41467-017-01310-z.

Abstract

Cellular protein homeostasis depends on heat shock proteins 70 kDa (Hsp70s), a class of ubiquitous and highly conserved molecular chaperone. Key to the chaperone activity is an ATP-induced allosteric regulation of polypeptide substrate binding and release. To illuminate the molecular mechanism of this allosteric coupling, here we present a novel crystal structure of an intact human BiP, an essential Hsp70 in ER, in an ATP-bound state. Strikingly, the polypeptide-binding pocket is completely closed, seemingly excluding any substrate binding. Our FRET, biochemical and EPR analysis suggests that this fully closed conformation is the major conformation for the ATP-bound state in solution, providing evidence for an active release of bound polypeptide substrates following ATP binding. The Hsp40 co-chaperone converts this fully closed conformation to an open conformation to initiate productive substrate binding. Taken together, this study provided a mechanistic understanding of the dynamic nature of the polypeptide-binding pocket in the Hsp70 chaperone cycle.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate
  • Binding Sites
  • Conserved Sequence
  • Crystallography, X-Ray
  • Glycine / metabolism
  • HSP40 Heat-Shock Proteins / metabolism
  • HSP70 Heat-Shock Proteins / chemistry*
  • HSP70 Heat-Shock Proteins / metabolism*
  • Heat-Shock Proteins / chemistry
  • Heat-Shock Proteins / metabolism
  • Humans
  • Models, Biological
  • Models, Molecular
  • Peptides / metabolism*
  • Protein Conformation
  • Substrate Specificity

Substances

  • HSP40 Heat-Shock Proteins
  • HSP70 Heat-Shock Proteins
  • Heat-Shock Proteins
  • Peptides
  • Adenosine Triphosphate
  • Glycine
  • molecular chaperone GRP78