Myosin is the major component of the thick filaments and most myosin molecules are composed of a head, neck, and tail domain; the myosin head binds to thin filamentous actin, and uses ATP hydrolysis to generate force and "walk" along the thin filament.

There are many cell-specific isoforms of myosin heavy chains, coded for by a multi-gene family.

[3] The 3-D structure of the head portion of myosin has been determined [4] and a model for the actin-myosin complex has been constructed.

The myosin head first attaches to actin together with the products of ATP hydrolysis, performs a power stroke associated with release of hydrolysis products, and detaches from actin upon binding with new ATP.

The detached myosin head then hydrolyses ATP, and performs a recovery stroke to restore its initial position.