Final answer:
Nucleotides bound to actin monomers are involved in the dynamic equilibrium of actin filament polymerization, with ATP-bound monomers adding to the filament and later becoming ADP-bound as ATP is hydrolyzed. This non-equilibrium process leads to treadmilling, where there is simultaneous growth and shrinkage of filament ends.
Step-by-step explanation:
What is true about nucleotides bound to actin monomers is that they play a crucial role in the dynamic process of actin filament polymerization and depolymerization. Actin monomers (G-actin) bind ATP and add to the plus end of the actin filament. Soon after, the ATP is hydrolyzed to ADP, which decreases the binding strength of the monomers and leads to filament instability.
This non-equilibrium process, where actin filaments constantly grow and shrink, is known as treadmilling. During treadmilling, there is a net addition of ATP-bound actin monomers at the plus end, and a concurrent loss of ADP-bound actin monomers at the minus end, which can result in a constant turnover of actin within the filament while maintaining overall filament length.
The polymerization of actin is a highly regulated process, which not only involves the nucleotide binding status but also regulatory proteins, such as alpha-actinin and myosin, that influence the structure and dynamical behavior of actin filaments in muscles and other cell types.