Definitions of F Actin
Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments ( known also as filamentous or F- actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or G- actin. In conjunction with MYOSINS, actin is responsible for the contraction and relaxation of muscle.