Some observations on the localization of myosin, actin and tropomyosin in the rabbit myofibril

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Abstract
Extraction of actin, tropomyosin and component C from isolated rabbit myofibrils was accompanied by a disappearance of the Z line, almost complete disappearance of material from the I band and a fall in density and widening of the H space. Pyrophosphate solutions and 5 m[image]-acetate buffer, pH 4.3, extracted practically all the myosin together with some actin and tropomyosin. On exhaustive treatment with these solutions the A band was removed from the sarcomere almost completely. In myofibrils isolated from fresh muscle the H space was apparent in sarcomeres of a wide range in lengths. No obvious correlation was apparent between the lengths of the I band and H space. It is concluded that myosin is absent from the I band and Z line and that actin and tropomyosin are present in both I and A bands.