Problem 7

Background and context

The profilin–ATP–actin complex binds to the (+) end efficiently, and profilin dissociates once the new actin subunit is bound. This activity of profilin does not improve treadmilling pace on its own, but it does offer a source of ATP-actin from released ADP-actin; as a result, almost all free G-actin in a cell has bound ATP. As one might expect, the cell uses signal transduction pathways to regulate profilin and cofilin, and so actin filament turnover.