Studies of Myosin in Hereditary Muscular Dystrophy in Mice*

Abstract

Myosin was isolated from mice with hereditary muscular dystrophy (strain 129, Jackson Memorial Laboratory) and from normal mice of the same strain. The following differences were observed 1) the myosin from dystrophic animals has a higher content of alanine, valine, and isoleucine and a lower content of glycine and histidine; 2) about 25% of the protein appeared to be large aggregates under conditions where the normal was almost entirely monomeric; 3) fewer of its SH groups reacted with sulfhydryl reagents than normal despite similar total cysteine content and similar number of SH-con-taining tryptic peptides; 4) it seemed less stable than normal on storage. It is suggested that the primary defect in muscular dystrophy of mice might be a genetic abnormality of the myosin molecule.