Composition of the myosins and myogen of skeletal muscle

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Abstract
The total N, amide N, total S, cystine, methionine, tyrosine and tryptophan of a series of myosins from skeletal muscle were detd. Except for minor analytical differences, mammalian and avian myosins possessed a uniform composition, but larger deviations were observed in the case of lobster and fish myosins. In all myosins analysed, the general order of magnitude of each amino-acid constituent was similar, and pointed to the existence of a fundamental amino-acid plan for the elaboration of these proteins. Rabbit myogen differed markedly in composition from rabbit myosin. The total disulphide content, expressed as cystine, of all myosins examined varied between 0.72 and 1.0% and the content of methionine between 3.35 and 3.65%. The avg. recovery of S in terms of total disulphide and methionine as a % of the S in the protein hydrolysate is 89%. Methionine was elaborated in preference to cystine, and the significance of this fact was discussed in relation to the properties of denatured myosin films which were structurally related to the labile supercontracting form of keratin. The tryptophan content of the myosins in comparison with those of other food proteins (e.g., casein and egg albumen) was relatively low.