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In Situ Monitoring of Transiently Formed Molecular Chaperone Assemblies in Bacteria, Yeast, and Human Cells
Published on: September 2, 2019
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ClpL is a functionally active tetradecameric AAA+ chaperone, distinct from hexameric/dodecameric ones
Gyuhee Kim1, Seong-Gyu Lee2,3, Seungsu Han1
1Department of Biological Sciences, Sungkyunkwan University, Suwon, Korea.
Summary
This study characterizes ClpL, a novel tetradecameric AAA+ chaperone from Streptococcus pneumoniae. Unlike typical hexameric/dodecameric forms, ClpL maintains a distinct functional tetradecameric structure crucial for its activity.
Area of Science:
- Molecular Biology
- Structural Biology
- Biochemistry
Background:
- ATPases associated with diverse cellular activities (AAA+) chaperones are vital for maintaining protein homeostasis.
- Their function is typically regulated by hexameric or dodecameric quaternary structures.
Purpose of the Study:
- To structurally and biochemically characterize ClpL, a tetradecameric AAA+ chaperone from Streptococcus pneumoniae.
- To elucidate the unique quaternary structure and functional implications of ClpL.
Main Methods:
- Cryo-electron microscopy (cryo-EM) to determine high-resolution structure.
- Small-angle X-ray scattering (SAXS) for solution structure analysis.
- Biochemical assays and site-directed mutagenesis to assess protein function and residue importance.
Main Results:
- ClpL forms a stable tetradecamer in the presence of ATP.
- Cryo-EM revealed a unique tetradecameric arrangement, distinct from known AAA+ chaperones.
- SAXS data suggest a spiral conformation, and specific residues (Q321, R670) are critical for heptameric ring assembly and overall function.
Conclusions:
- ClpL represents a functionally active tetradecameric AAA+ chaperone.
- Its distinct structure and assembly mechanism differentiate it from canonical hexameric/dodecameric AAA+ chaperones.
- This finding expands the known structural diversity and functional mechanisms of AAA+ chaperones.
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