Crystalline layers and three-dimensional structure of Staphylococcus aureus alpha-toxin

Area of Science:

• Microbiology
• Structural Biology
• Biophysics

Background:

• Alpha-toxin is a pore-forming protein from Staphylococcus aureus.
• Protein-lipid interactions are crucial for membrane protein function and assembly.

Purpose of the Study:

• To investigate the structural basis of alpha-toxin oligomerization induced by platelet lipids.
• To determine the oligomeric structure of alpha-toxin in crystalline arrays.

Main Methods:

• Electron microscopy and image processing were used to analyze crystalline areas.
• Crystallization was induced by interacting alpha-toxin with platelet lipids or lipid layers.
• Tetragonal symmetry and unit cell parameters were determined.

Main Results:

• Ordered domains of alpha-toxin crystals, up to micrometers in size, were observed.
• Crystals exhibited tetragonal symmetry, forming 2D sheets or 3D piles.
• The averaged alpha-toxin oligomer showed cyclic symmetry with a central cavity and four asymmetric units.

Conclusions:

• Alpha-toxin forms ordered crystalline arrays upon interaction with platelet lipids.
• The structural data suggests alpha-toxin binds to hydrophobic surfaces in a specific conformation.
• This interaction is key to understanding alpha-toxin's assembly and membrane activity.