Natural Actin and Tropomyosin from Molluscan Catch Muscle

In this work, the main proteins of thin filaments (actin and tropomyosin) were isolated from the catch muscle of the mussel Crenomytilus grayanus and the rabbit skeletal muscles. Rabbit actin and tropomyosin and mussel tropomyosin were isolated by traditional methods as opposed to "natural" mussel actin (isolation of the mussel actin from acetone powder is impossible). These proteins were used to reconstruct actin+tropomyosin complexes in nonhybrid and hybrid manner. A non-hybrid complex, reconstructed from rabbit actin and tropomyosin, has higher reduced viscosity than complex of mussel proteins where reduced viscosity was nearly indistinguishable from the intrinsic viscosity. ÐÂ’oth rabbit and mussel actin were purified by polymerization-repolymerization cycles followed by gel filtration chromatography. During purification, the viscosity of both actins increased, and the difference in viscosity between them decreased. Based on the SDS-electrophoresis, we did not find any of the other proteins in the chromatographic fractions, except actin. However, obtained chromatographic fractions have significant differences in viscosity and rate of polymerization. We believe that these properties caused by the presence of an "ending factor” (such as β-actinin or Cap Z) in actin preparations. The data obtained indicate that isolation of “natural” actin is accompanied by a coextraction of an unknown or known "ending factor" in amounts that may be greater than those obtained from the acetone powder of rabbit skeletal muscles.