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A new native EcHsp31 structure suggests a key role of structural flexibility for chaperone function.
Paulene M Quigley1, Konstantin Korotkov, François Baneyx
1Department of Biochemistry, Department of Chemical Engineering, and Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195-7742, USA.
Protein Science : a Publication of the Protein Society
|December 24, 2003
Summary
Heat shock protein Hsp31 in E. coli uses flexible loops to bind client proteins under stress. These loops expose hydrophobic patches at high temperatures and retract at lower temperatures, facilitating protein management.
Area of Science:
- Molecular biology
- Structural biology
- Biochemistry
Background:
- Heat shock proteins (HSPs) are vital for cellular survival during environmental stress.
- Hsp31 from Escherichia coli is a homodimeric protein with A and P domains, crucial for stress response.
- Hsp31 contains two catalytic triads per dimer, involving residues from both A and P domains.
Purpose of the Study:
- To elucidate the structural basis for Hsp31's function under stress.
- To investigate the role of flexible loops in Hsp31's chaperone activity.
- To confirm the arrangement of catalytic triads and dimer interface through new crystal structures.
Main Methods:
- X-ray crystallography to determine the structure of Hsp31 (Crystal Form II).
- Structural comparison between Crystal Form I and II to identify conformational changes.
- Analysis of conserved residues and surface properties related to protein-protein interactions.
Main Results:
- Crystal Form II confirmed the dimeric structure and catalytic triad arrangement of Hsp31.
- Increased flexibility in loops D2 and D3 was observed compared to Crystal Form I.
- Mobile loops D2 and D3 expose a conserved hydrophobic patch near the dimer interface, enhancing access to catalytic sites.
Conclusions:
- Hsp31 utilizes mobile loops D2 and D3 to bind client proteins via a hydrophobic patch at elevated temperatures.
- Upon temperature decrease, these loops retract, releasing client proteins and potentially aiding in their proper folding or degradation.
- The proposed mechanism of flexible loops in Hsp31 function may represent a general chaperone principle.