Comparative sequence of myosin light chains from normal and hypertrophied human hearts.

Myosin light chains from normal and hypertrophied human hearts were partially sequenced in order to see whether structural modifications of these light subunits could provide a molecular basis for the changes observed in heart properties and in myosin enzymatic activity. Normal light chains were prepared form hearts taken at autopsy, weighing 350 g or less and apparently devoid of myocardial disease. "Hypertrophied cardiac myosin light chains" were prepared from two greatly hypertrophied hearts, weighing 600 and750 g. No amino acid substitutions, deletions, or additions were observed in the light chains from hypertrophied hearts. The third light chain previously reported in human cardiac myosin and related to hypertrophy was found to be a proteolytic product of LC2. The comparison between human and beef cardiac myosin light chains indicated that the sequences of these subunits of the myosin molecule are highly conserved.