Related Experiment Videos
Conformational characterization of DnaK and its complexes by small-angle X-ray scattering
1Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064, USA.
Biochemistry
|March 12, 1996
Summary
Heat shock protein DnaK has a dumbbell shape, with its structure changing upon ATP binding. Substrate binding causes DnaK to return to its monomeric form, suggesting a cavity binding site.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- DnaK is a 70 kDa heat shock protein (hsp70) crucial for cellular protein homeostasis.
- Understanding DnaK's structure and conformational changes is key to its chaperone function.
Purpose of the Study:
- To characterize the structure of DnaK and its complexes using biophysical techniques.
- To investigate the conformational changes induced by nucleotide and substrate binding.
Main Methods:
- Small-angle X-ray scattering (SAXS) to determine overall structure and dimensions.
- Size-exclusion chromatography (SEC) to assess association states.
- Analysis of SAXS data using P(r) functions and Kratky plots.
Main Results:
- DnaK exhibits a dumbbell-shaped structure (dmax=112 Å) consistent with its two functional domains.
- ATP binding induces conformational changes, increasing Rg, Rs, and dmax.
- DnaK dimerization is sensitive to buffer and protein concentration; substrate binding promotes dissociation to monomeric form.
- Substrate binding likely occurs in a cavity, reducing the complex's Rg.
- The unfolding intermediate state adopts a compact, molten globule-like conformation.
Conclusions:
- DnaK's structure is adaptable and influenced by nucleotide and substrate binding.
- Substrate interaction involves specific binding sites, likely a cleft or cavity.
- DnaK's oligomerization state is dynamically regulated by cellular conditions and substrate presence.