Figure 5.

Illustration of the myosin powerstroke and two scenarios to explain the observed single fluorophore polarization data. See text for explanation. The fluorophore emission dipole on the RLC is depicted as an arrow on the myosin light chain domain with the essential light chain (ELC) also indicated. The multiple red arrows represent a dipole that has significant rotational freedom either caused by rotational freedom of the probe on the myosin molecule or by the probe being relatively fixed to the myosin molecule and that the myosin itself is free to rotate. The weakly bound state, characterized by rapid myosin attachment to and detachment from actin, is indicated by a small vertical two-headed arrow.