סקירה כללית של המבנה והתפקוד של מיוזין

Myosin is a superfamily of actin-based motor proteins, with prominent members myosin I and II.

Myosin I is a short monomeric protein with a globular head attached to the actin filaments and a short tail that binds vesicles and organelles for cargo transport.

Myosin II, found in the sarcomere of muscle cells, is a highly asymmetric dimer, consisting of six polypeptide subunits—two identical heavy chains and one pair each of essential and regulatory light chains.

The heavy chains have an N-terminal globular head domain with a nucleotide-binding site for ATPase activity, and an actin-binding site, for attaching to the actin filament.

Adjacent to the actin-binding domain is a flexible neck attached to the light chains that extend to a long alpha-helical C-terminal tail forming a coiled-coil structure.

The essential light chains maintain the stability of the coiled-coil tail of the heavy chains, while the regulating light chains help in the movement of the globular heads during cross-bridge formation with actin filaments during muscle contraction.