Assembly dynamics and structure of an aegerolysin, ostreolysin A6

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Ostreolysin A6 (OlyA6) is a mushroom protein that binds cell membranes.
• OlyA6, with its partner pleurotolysin B, forms a pore complex, but OlyA6 alone shows pro-apoptotic effects.
• Understanding OlyA6 assembly is key to its biological function and potential applications.

Purpose of the Study:

• To investigate the formation dynamics and structure of OlyA6 assembly on lipid membranes.
• To elucidate the role of specific membrane components in OlyA6 organization.
• To characterize the OlyA6 dimer structure involved in pore formation.

Main Methods:

• High-speed atomic force microscopy (HS-AFM) was used to observe OlyA6 assembly in real-time.
• Lipid membranes containing ceramide phosphoethanolamine and cholesterol were utilized as a model system.
• Molecular-level structural analysis of OlyA6 crystals was performed.

Main Results:

• OlyA6 dimers reorganized from random coverage to form 2D protein crystals on the membrane.
• Crystal growth occurred longitudinally, with hexameric OlyA6 repeat units forming a hexagonal unit cell.
• The precise arrangement of dimers within the crystal and the structure of the pore-forming dimer were determined.

Conclusions:

• OlyA6 undergoes a dynamic self-assembly process on specific lipid membranes, forming ordered crystalline structures.
• The determined crystal structure provides insights into the mechanism of OlyA6-mediated pore formation.
• This study clarifies the structural basis for OlyA6's interaction with membranes and its partner protein, pleurotolysin B.