Isolation from bovine brain of tropomyosins that bind to actin filaments with different affinities.

Tropomyosin was isolated from bovine brain using mild conditions thereby avoiding heat precipitation. Separation by DEAE ion exchange chromatography yielded a 33 kDa tropomyosin and a mixture of 30 and 32 kDa tropomyosin. Binding of the tropomyosins to actin filaments was measured by a newly developed method. The binding was assayed by the retarding effect of tropomyosin on actin polymerization. The 33 kDa tropomyosin was found to bind to actin filaments with considerably higher affinity than the 30 and 32 kDa tropomyosin.