The content of troponin, tropomyosin, actin, and myosin in rabbit skeletal muscle myofibrils

A stacking sodium dodecyl sulfate polyacrylamide gel electrophoresis system has been used to resolve and quantify all the major myofibrillar protein components (actin, myosin, tropomyosin, and troponin C, T, and I). Quantification was achieved by densitometry of the fast green-stained gels calibrated with the use of purified proteins. The approximate molar ratios of these proteins in rabbit muscle are: actin: myosin: tropomyosin: troponin T: troponin I: troponin C = 7:1:1:1:1:1. On the basis of these results and available structural information one obtains an estimate of 254 myosin molecules per thick filament.