Modification of the alkali light chains of skeletal myosin inhibits actin binding and adenosine triphosphate cleavage.

Heavy meromyosin treated with the ATP analog, 6,6'-dithiobis(inosinyl-5'-yl imidodiphosphate), (slppNHp)2, in the presence of adenyl-5'-yl imidodiphosphate at 0 degrees loses its EDTA-ATPase activity and actin binding ability in a parallel manner. Studies with myosin show that under the above conditions (slppNHp)2 reacts preferentially with the single cysteines of the alkali light chains (Mr = 20,700 and 16,500) suggesting a role for these subunits in regulating actin-myosin interaction and ATP cleavage.