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Related Experiment Videos

Structural analysis of substrate binding by the molecular chaperone DnaK

X Zhu1, X Zhao, W F Burkholder

  • 1Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York 10032, USA.

Science (New York, N.Y.)
|June 14, 1996
PubMed
Summary

Heat shock protein DnaK binds unfolded proteins to aid folding. Its crystal structure reveals a latch mechanism in conformation-dependent substrate binding for stable complexes.

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Area of Science:

  • Molecular Biology
  • Structural Biology
  • Biochemistry

Background:

  • Heat shock proteins (HSPs), including DnaK (a 70-kilodalton heat-shock protein, hsp70), are crucial for protein homeostasis.
  • Hsp70 family members facilitate protein folding, interaction, and translocation by binding unfolded polypeptide segments.
  • These proteins possess two domains: a substrate-binding domain and an adenosine triphosphatase (ATPase) domain.

Purpose of the Study:

  • To determine the crystal structure of the DnaK substrate-binding domain complexed with a peptide.
  • To elucidate the structural basis of substrate binding and the mechanism of DnaK function.

Main Methods:

  • X-ray crystallography was employed to determine the structure of the DnaK peptide complex.
  • High-resolution (2.0 angstroms) structural analysis was performed on the crystallized complex.

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Main Results:

  • The crystal structure reveals the substrate-binding unit of DnaK comprises a beta-sandwich subdomain and alpha-helical segments.
  • A bound peptide adopts an extended conformation within a channel formed by loops of the beta-sandwich subdomain.
  • An alpha-helical domain stabilizes the complex without direct peptide contact, exhibiting rotational flexibility in different crystal lattices.

Conclusions:

  • The determined structure provides atomic-level insight into how DnaK binds unfolded polypeptides.
  • The observed conformational flexibility suggests a model for conformation-dependent substrate binding involving a latch mechanism.
  • This mechanism likely contributes to the formation of long-lived complexes essential for protein folding and cellular stress response.