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ATP hydrolysis induces an intermediate conformational state in GroEL
A Galán1, O Llorca, J M Valpuesta
1Department de Bioquímica y Biología Molecular, Unidad asociada al CSIC, Universidad del París Vaco, Bilbao, Spain.
European Journal of Biochemistry
|January 23, 1999
Summary
The molecular chaperone GroEL undergoes distinct conformational changes upon nucleotide binding. ATP hydrolysis induces a unique intermediate state, exposing hydrophobic surfaces, unlike ADP or AMP-PNP binding.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Dynamics
Background:
- Molecular chaperones like GroEL are essential for protein folding.
- Understanding GroEL's conformational states is key to its function in protein homeostasis.
Purpose of the Study:
- To investigate the conformational properties of GroEL in the presence of ATP, ADP, and AMP-PNP.
- To elucidate the structural differences induced by nucleotide binding and hydrolysis.
Main Methods:
- Differential scanning calorimetry (DSC) for thermal stability analysis.
- Fourier-transform infra-red (FT-IR) spectroscopy for secondary structure assessment.
- Fluorescence spectroscopy using 8-anilino-naphthalene-1-sulfonate (ANS) to probe hydrophobic surfaces.
Main Results:
- Nucleotide binding to one GroEL ring decreases thermal transition temperature (Tm), reversed when both rings are occupied.
- ATP binding induces a reversible low-temperature endotherm and enhanced ANS binding, dependent on ATP hydrolysis.
- GroEL exhibits a distinct conformational state during ATP hydrolysis, differing from ADP or AMP-PNP bound states.
Conclusions:
- Sequential nucleotide binding to GroEL's rings differentially affects its thermal denaturation.
- ATP hydrolysis triggers a unique GroEL conformation characterized by altered tertiary and quaternary structures and exposed hydrophobic surfaces.
- This study provides insights into the dynamic conformational changes of GroEL crucial for its chaperone activity.