The protein actin is one of the fundamental cytoskeletal polymers responsible for intracellular movement and various biochemical processes.  By utilizing filopodia, membrane protrusions comprised of actin filaments, cells are capable of locomotion.  Filopodia growth is regulated by formins, a class of accessory proteins that influence the principle stage of actin filament assembly.  Specifically, the formin FMNL3 contains formin homology 2 (FH2) domain necessary for filopodia production.  The biochemical activities involved in cell motility can be understood through the discovery and analysis of the FMNL3 FH2/TMR-actin structure.  By performing site-directed mutagenesis, preparing and purifying protein, and assessing binding via gel filtration, the residues responsible for the binding of FMNL3 FH3 and TMR-actin were determined,  Although the majority of the residues mutated were not independently required for binding, filopodia and elongation assays were indicative of their purpose.  Structural analysis of the FMNL3-actin complex, as well as solving the structure of the FMNL3 C-terminus via X-Ray crystallography, will further our understanding of the cellular network and the foundation of cell movement.

Mutational analysis of the FH2 domain of the mammalian formin FMNL3 bound to TMR-actin

243rd National Meeting (2012)

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