Metabolism of myosin and life time of myofibrils

Abstract

Myosin was isolated at various times after the injection of radiol-active glycine into groups of rats on a diet containing 24% of protein. Its specific activity (and that of the glycine it contained) remained constant for about 30 days and then decreased. The ratio of the specific activity of the myosin to that of erythrocyte globin was constant from 5 to 30 days after injection. On this basis the average life span of the myofibril was considered to be 30 days. When the animals received a diet containing 45% of protein the radioactivity of the myosin progressively decreased, showing that the protein undergoes turnover.