© 1971 by The Society for Integrative and Comparative Biology
Contractile Proteins of a Benthic Fish. III. Subunit Composition of Myosin
Deparlment of Medicine and Program in Biophysics, State University of New York Downstate Medical Center Brooklyn, Neic York 11203
Department of Physiology, University of California Los Angeles, California 90024
SYNOPSIS. Ultracentrifugal and electrophoretic experiments are reported on the subunit composition of myosin from skeletal muscle of a benthic fish, Coryphaenoides species. Coryphaenoides myosin undergoes extensive association in concentrated KGI solutions at neutral pH, but sedimentation equilibrium experiments indicate the presence of a small fraction (3%) of monomeric myosin with molecular weight approximately 440,000. At pH 11, some of the aggregated myosin is dissociated, and monomeric myosin is itself dissociated into a heavy component (410,000 mol wt) and a light component (14,000 mol wt) that comprises 5–7% of the protein. The lialkali component of Coryphaenoides myosin yields a single predominant band on cellulose acetate electrophoresis and SDS-urea electrophoresis in 9% acrylamide gel. The stoichiometric evidence indicates that Coryphaenoides myosin contains two heavy chains (205,000 mol wt) and two light chains (14,000 mol wt) that are equivalent with respect to net electrostatic charge and molecular weight. Preparations of myosin obtained by direct extraction from muscle mince and by dissociation of actomyosin extracted from muscle mince also contain 5% of a 47,000 mol wt component presumably actin), traces of 34–36,000 mol wt component, and about 5.7% of low molecular weight material (10,000–15,000) that probably represents contaminant protein, although the possibility of denatured nivosin subunits cannot be excluded.