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The three-dimensional structure of trypsin-treated Staphylococcus aureus alpha-toxin.
A Olofsson1, U Kavéus, M Thelestam
1Center for Structural Biochemistry, Karolinska Institutet, Huddinge, Sweden.
Journal of Structural Biology
|May 1, 1992
Summary
Trypsin treatment inactivates staphylococcal alpha-toxin by cleaving it. Structural analysis reveals conformational changes in a hinge region, crucial for membrane permeabilization.
Area of Science:
- Structural biology
- Microbiology
- Biochemistry
Background:
- Staphylococcal alpha-toxin is a critical virulence factor.
- Understanding its structure-function relationship is key to developing inhibitors.
Purpose of the Study:
- To determine the 3D structure of trypsin-cleaved staphylococcal alpha-toxin.
- To investigate the conformational changes associated with toxin inactivation and membrane permeabilization.
Main Methods:
- Electron microscopy and image processing of negatively stained crystals.
- 3D reconstruction to 23 Å resolution.
- Comparison with native alpha-toxin structure.
Main Results:
- Tryptic cleavage yields two fragments, inactivating the toxin.
- Oligomeric arrays formed on lipid layers resemble native structures.
- 3D structure shows separated subdomains, confirming previous findings.
- Cleavage occurs in a putative hinge region, suggesting its role in conformational changes.
- Refined projection map at ~10 Å resolution obtained.
Conclusions:
- Tryptic cleavage induces conformational changes in a hinge region of staphylococcal alpha-toxin.
- These changes are consistent with the mechanism of membrane permeabilization.
- Structural insights provide a basis for understanding toxin function and inhibition.