The study identifies a 26S RNA fraction from chick muscle polysomes that contains the messenger RNA coding for the large subunit of myosin, advancing the understanding of myofibrillar protein biosynthesis.
Although a great deal is known concerning the chemistry and function of the contractile proteins, it has been only recently that progress has been made in attempts to gain a detailed understanding of the biosynthesis of these proteins. It is our ultimate goal to elucidate the control mechanisms involved in myofibrillar protein synthesis, to understand the role of these mechanisms in the development of muscle, and to establish the relationship between the synthesis of these proteins and their ultimate assembly into the contractile apparatus. Although we are currently working on the synthesis of many of the structural proteins of chick muscle, the relative ease by which poly-somes synthesizing myosin heavy chain can be isolated on sucrose density gradients (Heywood and Rich, 1968) has led us to analyze myosin synthesis in some detail. An RNA fraction, sedimenting at approximately 26S, can be extracted from the large myosin-synthesizing polysomes. This RNA fraction has been shown by a number of criteria to contain messenger RNA (mRNA) coding for the large molecular weight subunit (200,000) of myosin
Morris et al. (Mon,) studied this question.