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Visualization of substrate binding and translocation by the ATP-dependent protease, ClpXP
J Ortega1, S K Singh, T Ishikawa
1Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Molecular Cell
|February 13, 2001
Summary
The E. coli ClpXP protease binds protein substrates via its ClpX component. ATP then drives substrate unfolding and translocation into the ClpP protease for degradation.
Area of Science:
- Molecular Biology
- Structural Biology
- Biochemistry
Background:
- The ClpXP system is a crucial ATP-dependent protease in E. coli.
- Understanding substrate binding and translocation is key to elucidating protease function.
Purpose of the Study:
- To investigate the mechanism of protein substrate binding and internalization by the E. coli ClpXP protease complex.
Main Methods:
- Electron microscopy was used to visualize ClpXP complexes with and without substrate.
- ATP and non-hydrolyzable ATP analogs were employed to study conformational changes.
Main Results:
- A narrow axial channel in ClpX and protrusions on its surface were observed.
- Substrate lambda O protein bound to the ClpX surface, disappeared upon ATP addition (degradation), and translocated into ClpP in inactive complexes.
Conclusions:
- Substrates bind to specific sites on the ClpX ATPase.
- ATP hydrolysis facilitates substrate unfolding and translocation into the ClpP core for degradation.