Final answer:
A shift in the concentration/activity of actin-binding proteins, particularly motor proteins like myosin, can cause a shift in the equilibrium between actin monomers and polymers, affecting actin polymerization and the cell's motility.
Step-by-step explanation:
The question pertains to the effect of protein concentration/activity on the equilibrium between actin monomers and polymers. Actin is a protein that forms filaments within the cytoskeleton of eukaryotic cells. The equilibrium between monomeric (G-actin) and polymeric actin (F-actin) is a non-equilibrium process in the presence of ATP.
Actin-binding proteins, such as myosin motors and capping proteins, regulate actin dynamics by affecting the rate of polymerization and depolymerization at the plus and minus ends of actin filaments. Changes in activities of motor proteins like myosin produce conformational changes in actin filaments, impacting their polymerization and resulting in cell motility.
Additionally, crosslinking proteins like alpha-actinin affect the mechanical properties of actin networks in cells by altering their elastic response and stability. Dynamical models including variables such as on and off rates of monomer association help to understand the actin filament behavior under different cellular conditions.