Actins

**Definition:** 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.

**Tree numbers:** - D05.750.078.730.250 - D12.776.210.500.100 - D12.776.220.525.255

**Synonyms:** - Actin