Competition between anion binding and dimerization modulates Staphylococcus aureus phosphatidylinositol-specific
Jiongjia Cheng1, Rebecca Goldstein, Boguslaw Stec
1Department of Chemistry, Boston College, Chestnut Hill, MA 02467, USA.
The Journal of Biological Chemistry
|October 6, 2012
Summary
Staphylococcus aureus phosphatidylinositol-specific phospholipase C (PI-PLC) activity is controlled by dimerization. Phosphatidylcholine enhances PI-PLC activity by promoting dimerization, while anions inhibit it by binding to a separate site.
Area of Science:
- Biochemistry
- Microbiology
- Structural Biology
Background:
- Bacterial phosphatidylinositol-specific phospholipase C (PI-PLC) targets eukaryotic PI and GPI-linked proteins.
- PI-PLC is a secreted virulence factor in Staphylococcus aureus.
Purpose of the Study:
- To elucidate the structural basis and regulatory mechanisms of S. aureus PI-PLC activity.
- To investigate the role of protein dimerization and anion binding in PI-PLC function.
Main Methods:
- X-ray crystallography to determine the homodimeric structure of S. aureus PI-PLC.
- Enzyme kinetics and mutagenesis studies to assess the functional relevance of structural findings.
- Investigated the effect of phosphatidylcholine and anions on enzyme activity.
Main Results:
- A novel crystal structure revealed that S. aureus PI-PLC forms a dimer via helix B, crucial for membrane binding and optimal activity.
- Enzyme kinetics demonstrated that phosphatidylcholine enhances PI-PLC activity by facilitating dimerization.
- Mutagenesis confirmed that phosphatidylcholine acts by reducing anionic lipid interactions with a cationic pocket, stabilizing the monomer.
Conclusions:
- S. aureus PI-PLC activity is modulated by a unique mechanism involving competition between soluble anion binding and transient membrane dimerization.
- Anion binding to a discrete site antagonizes activating transient dimerization.
- Protein oligomerization and anion binding interplay to control enzyme activity.
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