Cooperative effects of tropomyosin on the dynamics of the actin filament.

Sofia Khaitlina, Olga Tsaplina, Horst Hinssen

FEBS letters 2017 Jul

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Tropomyosin (Tpm) plays an important role in regulating the organisation and functions of the actin cytoskeleton. Here, we describe a new approach to analyse the effects of Tpm on actin dynamics. Using F-actin proteolytically modified within the DNase-binding loop (ECP-actin), we show that Tpm binding almost completely suppresses the increased subunit exchange intrinsic for this F-actin. The effect is both concentration-dependent and cooperative, with half-maximal inhibition observed at about a 1 : 50 Tpm : actin ratio. Tpm decreases not only the number concentration of ECP-actin filaments, but also the rate of the filament subunit exchange. Our data suggest that Tpm regulates the dynamics of actin filaments by an allosteric strengthening of intermonomer contacts in the actin filament, and that this mechanism may be involved in the modulation of cytoskeletal dynamics. © 2017 Federation of European Biochemical Societies.

Citation

Sofia Khaitlina, Olga Tsaplina, Horst Hinssen. Cooperative effects of tropomyosin on the dynamics of the actin filament. FEBS letters. 2017 Jul;591(13):1884-1891