Light chain phosphorylation alters the N terminal structure of gizzard myosin heavy chain in an ATP dependent manner.

It was shown that the heavy chain structure was altered by the phosphorylation of light chain in gizzard myosin. Phosphorylated myosin was compared with unphosphorylated myosin with respect to the chymotryptic fragmentation with or without ATP in the medium. The rise and fall of the fragments were well explained by the reconstitution model for unphosphorylated myosin (Okamoto, Y., et al. (1980) J. Biochem. 88, 361-371). A specific cleavable site in the myosin head was completely abolished by the phosphorylation of light chain. The effect of phosphorylation on the site could be observed in the absence of ATP but not in its presence. These results strongly suggest the possible integrity of the site, 5K daltons apart from the masked N terminus, for the physiological activity of gizzard myosin.