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.

Synonyms: Isoactin, G Actin, N Actin, Actins, N-Actin, gamma Actin, F Actin, 0, alpha Isoactin, F-Actin, beta-Actin, gamma-Actin, Actin, G-Actin, beta Actin, alpha Actin, alpha-Actin, alpha-Isoactin