An alpha-actinin-profilin chimaera with two alternatively operating actin-binding sites

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Actin dynamics are crucial for cellular processes.
• Actin-binding proteins regulate actin polymerization and filament formation.
• Understanding protein-protein interactions in the actin cytoskeleton is essential.

Purpose of the Study:

• To construct and characterize a novel chimeric protein combining profilin and alpha-actinin.
• To investigate the dual actin-binding capabilities of the chimeric protein.
• To elucidate the functional interplay between different actin-binding domains.

Main Methods:

• Gene fusion and expression in Escherichia coli.
• Purification of chimeric protein using affinity chromatography.
• Biochemical assays, viscometry, and high-resolution electron microscopy.
• Analysis of actin polymerization kinetics and protein-actin interactions.

Main Results:

• The chimeric protein alphaA1-2P, comprising bovine profilin I and Dictyostelium discoideum alpha-actinin's actin-binding domain, was successfully constructed and purified.
• Both domains within the chimera were shown to be biologically active, binding poly-L-proline and inhibiting G-actin polymerization.
• The chimera exhibited enhanced inhibition of actin polymerization compared to parental profilin and demonstrated a switchable binding affinity for G-actin and F-actin.

Conclusions:

• The chimeric protein alphaA1-2P effectively combines the functions of profilin and alpha-actinin.
• The alpha-actinin domain preferentially binds to F-actin, decorating filaments laterally.
• This molecule can transition between binding monomeric G-actin and filamentous F-actin, providing a unique tool to study actin dynamics.