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Substrate transfer from the chaperone Hsp70 to Hsp90
Harald Wegele1, Sebastian K Wandinger, Andreas B Schmid
1Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
Journal of Molecular Biology
|January 13, 2006
Summary
Heat shock protein 70 (Hsp70) captures unfolded proteins, while heat shock protein 90 (Hsp90) requires co-chaperones like Ydj1 for efficient client protein folding. This reveals key steps in chaperone-mediated protein maturation.
Area of Science:
- Molecular Biology
- Protein Folding
- Cellular Chaperone Systems
Background:
- Heat shock proteins (Hsp90) are crucial for eukaryotic protein folding and maturation.
- Hsp90 functions with Hsp70, facilitated by adaptor proteins like Hop (Sti1 in yeast).
- Understanding client protein transfer between Hsp70 and Hsp90 is vital for cellular regulation.
Purpose of the Study:
- To elucidate the molecular mechanism of client protein transfer within Hsp70/Hsp90 chaperone complexes.
- To define the pathway of luciferase folding mediated by the Hsp70/Hsp90 system.
Main Methods:
- Analysis of luciferase folding using in vitro chaperone systems.
- Comparison of chaperone activity with and without Hsp90, Ydj1, and Sti1.
- Investigation of yeast and human chaperone systems.
Main Results:
- Hsp70 efficiently captures unfolded proteins, whereas Hsp90 shows low capture efficiency.
- Hsp70, Ydj1, and Sti1 exhibit chaperone activity towards luciferase in Hsp90's absence.
- Hsp90 requires Ydj1 for positive effects; without it, luciferase remains inactive on Hsp90.
- Similar results were observed in both yeast and human chaperone systems.
Conclusions:
- The study defines a pathway for luciferase folding within the Hsp70/Hsp90 chaperone system.
- Ydj1 is essential for Hsp90's function in client protein maturation.
- Conserved mechanisms exist for Hsp70/Hsp90 chaperone interactions across species.