Myosin

Myosin is a family of actin-associated motor proteins that couple ATP hydrolysis to mechanical work. Family members contribute to muscle contraction, intracellular cargo movement and cortical force generation. Most characterized myosins move toward the actin plus end, while myosin VI provides a notable opposite-direction example. Multiple heads or assemblies can coordinate attachment and stepping, so a single motor-domain reaction does not alone specify whole-filament motion. ^[ref][ref]

The ability of a motor assembly to take repeated steps along actin before dissociating, often requiring coordination of multiple actin-binding heads.

A mechanically productive transition coupled to changes in nucleotide and actin binding. Load and isoform affect its detailed kinetics.

The neck-associated structural element that amplifies conformational changes in the motor domain into displacement.

Bound light chains help stabilize this elongated region. Changing lever-arm geometry can change step size without requiring a corresponding change in the distance of every chemical event at the ATP-binding site. ^[ref]

The fraction of an ATPase cycle spent strongly bound to actin. It contributes to processivity and tension holding but does not alone determine cellular function.

An unconventional actin-based motor whose movement is toward the pointed end, opposite the direction of most characterized myosins.

A class of actin-based cargo motors; well-studied dimeric members coordinate their heads for processive stepping.

Coordination allows one head to remain associated while the other advances, supporting repeated motion along actin. Single-fluorophore localization experiments distinguish this alternating-head mechanism from a model in which the same head always leads. ^[ref]

Myosin II participates in the actomyosin ring of typical animal cytokinesis.^[ref]