DIFFERENTIAL BINDING OF MYOSIN SUBFRAGMENT ONE SPECIES TO IMMOBILIZED ADP, AND ACTIN - INFLUENCE OF THE ALKALI LIGHT-CHAINS

Isolated myosin head regions (subfragments 1) have been prepared from a number of muscle types, and studied by affinity chromatography upon immobilized ADP and actin matrices. It has been shown that the two alkali light chain isoenzymes of subfragment 1 specific for a given skeletal muscle can be fractionated; therefore, these procedures provide essentially simple and rapid methods for the preparation of myosin head populations which are homogeneous with regard to their light chain content, and readily amenable to further study. Fractionation of slow twitch skeletal subfragment 1 species upon immobilized actin extends previous findings with fast twitch species [Winstanley, Trayer and Trayer (1977) FEBS Lett.77, 239–2421. In each case the heads containing the less anodic alkali light chain bind more tightly to the actin matrix. These results are supported by kinetic data which show differences only in the apparent Kmfor actin between the two acto‐subfragment 1 MgATPase. Comparison between the subfragment 1 species from different muscle types indicates a correlation between the strength of the interaction between subfragment 1 and immobilized actin and the myosin ATPase activity and contractile properties of the muscle. Tighter actin binding is associated with the low‐ATPase‐activity myosins characteristic of slow twitch skeletal and cardiac muscles. A possible relationship is suggested between the amino acid composition of the alkali light chain present, and the actin binding properties of the myosin head. Copyright © 1979, Wiley Blackwell. All rights reserved