Myosins belong to a superfamily of actin-based motor proteins comprising to date at least 15 classes. Myosin I (also designated myosin-1c, myo1c, M1C, myr 2 and myh 2) is a widely distributed single-headed myosin composed of an N-terminal motor domain, a calmodulin-light chain binding neck region, and a short C-terminal domain. In mammalian cells, myosin I is usually found in the cytoplasm and is especially enriched in perinuclear regions and dynamic cell margins. Myosin Iβ is found in a variety of cells such as kidney tubular cells and inner-ear hair cells.
Myosin I is involved in cell motility, microvilli anchorage, vesicular and organelle transport and signal transduction. Myosin I associate with lipid membranes through its tail domain while its motor domain interacts with actin filaments. Myosin Iβ (nuclear) co-localizes with RNA polymerases I and II and possibly acts as a molecular motor to power transcription.
