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Structural changes in GroEL effected by binding a denatured protein substrate
S Falke1, M T Fisher, E P Gogol
1Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
Journal of Molecular Biology
|May 15, 2001
Summary
The Escherichia coli chaperonin GroEL binds denatured glutamine synthetase (GS), altering its structure. Electron microscopy reveals GroEL conformational changes, including apical domain movements and substrate protrusion, upon GS binding.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- The Escherichia coli chaperonin GroEL facilitates protein folding by binding non-native proteins.
- GroEL prevents protein aggregation and misfolding in the absence of nucleotides or cofactors.
Purpose of the Study:
- To investigate the conformational changes in the GroEL tetradecamer upon binding of denatured glutamine synthetase (GS).
- To characterize the structure of GroEL-GS complexes using electron microscopy.
Main Methods:
- Electron microscopy was used to examine GroEL-GS complexes.
- Three-dimensional reconstruction was performed to determine the structure of the complex.
Main Results:
- GroEL-GS complexes exhibited heterogeneity due to incomplete GS loading.
- Binding of GS induced conformational changes in GroEL, including inward movement of apical domains and substrate protrusion.
- Chirality was observed in the heptameric projection of GroEL-GS, distinct from unliganded GroEL.
Conclusions:
- GS binding induces a distinct conformation in GroEL, affecting both cis and trans rings.
- Structural alterations include apical domain repositioning and changes in ring opening dimensions.
- These findings elucidate the mechanism of substrate binding and conformational changes in GroEL chaperones.