Final answer:
The best characterized factors of actin filament nucleation factors include the growth and shrinkage of actin polymers, the binding of ATP to monomeric (globular) actin, and the role of motor proteins like myosin in muscle contraction.
Step-by-step explanation:
The best characterized factors of actin filament nucleation factors include the growth and shrinkage of actin polymers, the binding of ATP to monomeric (globular) actin, and the role of motor proteins like myosin in muscle contraction. Actin filaments are composed of two intertwined strands of actin, each formed by actin monomers. The growth and shrinkage of actin filaments is regulated by the binding of ATP and its hydrolysis to ADP.