Final answer:
Formin promotes the nucleation of new actin filaments by facilitating the addition of actin monomers at the plus end of the filament, which is vital for various cell functions.
Step-by-step explanation:
The protein formin attaches to the growing end of an actin filament and promotes the nucleation of new actin filaments. Formin plays a crucial role in the polymerization of actin by facilitating the addition of new actin monomers at the plus end (++), leading to the growth of the filament. In contrast to nucleation, formin does not promote the severing, stabilization directly in the sense of preventing dissociation, nor depolymerization of actin filaments. The dynamic process of actin polymerization involves ATP hydrolysis which initiates a series of conformational changes, making filament growth at the plus end (++) faster than at the minus end (--), a process known as treadmilling. This non-equilibrium state of actin filament turnover is critical for various cellular processes including cell motility and division, muscle contraction, and stabilization of cell structures like microvilli and filopodia.