PHOTOCHEMICAL CLEAVAGE OF MYOSIN HEAVY CHAIN AND THE EFFECT ON THE INTERACTION WITH ACTIN

Myosin from rabbit skeletal muscle has been photochemically cleaved in the presence of vanadate ion and ATP. Two cleavage sites termed V1 and V2 within the S1 head region were studied. In the presence of magnesium ion both sites were cleaved, but in the absence of divalent cation cleavage only occurred at the V2 site. V2 cleaved myosin had higher K+-EDTA-ATPase and actin activated Mg2+-ATPase activity than V1, V2 cleaved myosin. Immunochemical characterization shows that the photochemical cleavage is more specific than that of proteolytic cleavage since breakdown of light chains was not observed for the photochemical method. This must be one of the best ways to prepare a single site cleaved myosin for the study of molecular mechanism of sliding.