Functional sequences of the myosin head

Muscle contraction originates from the sliding of myosin filaments on actin filaments, the energy for which is supplied by the hydrolysis of adenosine-5-triphosphate (ATP) by myosin. The nucleotide first binds to the acto-myosin complex in the myosin head (or subfragment-1), producing a conformational change which induces actin dissociation. The release of phosphate (Pi) then allows a return to the strong actin-myosin association, corresponding to the rigor state.