A mutant affecting the heavy chain of myosin in Caenorhabditis elegans

A set of non-complementing, closely linked, ethyl methanesulphonate-induced mutations in Caenorhabditis elegans specifically affects the structure and function of body-wall muscle cells but not the pharyngeal musculature. One of these mutations, e675, is semidominant and results in the production of a new protein of about 203,000 molecular weight in addition to normal myosin at about 210,000 M_r. The abnormal polypeptide chain is structurally very similar to normal myosin heavy chain when maps of iodinated peptides are compared.The E675 mutant shows a clear relation between defective movement, disruption of the body-wall muscle structure, and the molecular defect in the myosin heavy chains. The altered chain is synthesized in heterozygotes, suggesting that the e675 mutation is either in a structural gene for the heavy chain or in a cis acting control element. The hypothesis that there are two classes of myosin heavy chain within the same cells is discussed.