Molecular weight of tropomyosin from rabbit muscle

Abstract

Tropomyosin from rabbit skeletal muscle was entirely homogeneous in the ultracentrifuge. The molecular wt. in salt solns. ([mu] - 0.267) was 88,000 by osmotic pressure and 92,700 by sedimentation-diffusion; the value derived from the histidine content was 90,000 and the mean of all values, 90,500. The osmotic pressure and diffusion constant (and thus probably the sedimentation constant) were markedly dependent upon protein concn. At the lowest concn. investigated (0.6%), the frictional ratio was 3.1, indicating a very asymmetric molecule. The partial specific volume (0.71) was lower than that calculated from amino-acid residues (0.735).