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Capping protein binding to S100B: implications for the tentacle model for capping the actin filament barbed end
1Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110, USA.
The Journal of Biological Chemistry
|January 23, 2004
Summary
S100B protein binds to a peptide from capping protein, but not intact capping protein. This suggests the capping protein
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Interactions
Background:
- S100B is a calcium-binding protein.
- Capping protein regulates actin filament length.
- A proposed model suggests the alpha-subunit C terminus acts as a flexible 'tentacle'.
Purpose of the Study:
- To investigate the interaction between S100B and heterodimeric capping protein.
- To test the 'tentacle' model of capping protein structure and function.
Main Methods:
- Solution-based binding assays (using peptides and fusion proteins).
- Nuclear Magnetic Resonance (NMR) and X-ray crystallography.
- Analysis of capping protein activity.
Main Results:
- S100B binds to a synthetic peptide of the capping protein alpha-subunit C terminus.
- S100B does not bind to intact capping protein or affect its actin capping activity.
- Structural analysis reveals the C-terminal region is integrated into the native protein structure, not a free tentacle.
Conclusions:
- The 'tentacle' model for capping protein is not supported by these findings.
- The alpha-subunit C terminus is likely not mobile in native capping protein.
- Detergent addition can disrupt hydrophobic interactions, allowing weak S100B binding to capping protein.