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Study of Regulatory Effect of Tropomyosin on Actin–Myosin Interaction in Skeletal Muscle by in vitro Motility Assay

G. V. Kopylova, D. V. Shchepkin, and L. V. Nikitina*

Institute of Immunology and Physiology, Ural Division of the Russian Academy of Sciences, ul. Pervomaiskaya 91, 620041 Ekaterinburg, Russia; fax: (343) 374-0070; E-mail: l.nikitina@iip.uran.ru

* To whom correspondence should be addressed.

Received June 6, 2012; Revision received October 9, 2012
The interaction between myosin and actin in striated muscle tissue is regulated by Ca2+ via thin filament regulatory proteins. Skeletal muscle possesses a whole pattern of myosin and tropomyosin isoforms. The regulatory effect of tropomyosin on actin–myosin interaction was investigated by measuring the sliding velocity of both actin and actin–tropomyosin filaments over fast and slow skeletal myosins using the in vitro motility assay. The actin–tropomyosin filaments were reconstructed with tropomyosin isoforms from striated muscle tissue. It was found that tropomyosins with different content of α-, β-, and γ-chains added to actin filaments affect the sliding velocity of filaments in different ways. On the other hand, the sliding velocity of filaments with the same content of α-, β-, and γ-chains depends on myosin isoforms of striated muscle. The reciprocal effects of myosin and tropomyosin on actin–myosin interaction in striated muscle may play a significant role in maintenance of effective work of striated muscle both during ontogenesis and under pathological conditions.
KEY WORDS: skeletal myosin isoforms, tropomyosin isoforms, in vitro motility assay

DOI: 10.1134/S0006297913030073