Calponin-Like Protein from Mussel Smooth Muscle Is a Competitive Inhibitor of Actomyosin ATPase

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V. V. Sirenko¹, A. V. Dobrzhanskaya², N. S. Shelud’ko², and Y. S. Borovikov^1*

¹Institute of Cytology, Russian Academy of Sciences, 194064 St. Petersburg, Russia; fax: +7 (812) 247-0341; E-mail: boroviko@mail.cytspb.rssi.ru

²Zhirmunsky Institute of Marine Biology, Far Eastern Division, Russian Academy of Sciences, 690041 Vladivostok, Russia; fax: +7 (423) 231-0900; E-mail: sheludko@stl.ru

^* To whom correspondence should be addressed.

Received April 13, 2015; Revision received July 23, 2015

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The goal of this work was to elucidate the mechanism of inhibition of the actin-activated ATPase of myosin subfragment-1 (S1) by the calponin-like protein from mussel bivalve muscle. The calponin-like protein (Cap) is a 40-kDa actin-binding protein from the bivalve muscle of the mussel Crenomytilus grayanus. Kinetic parameters V_max and K_ATPase of actomyosin ATPase in the absence and the presence of Cap were determined to investigate the mechanism of inhibition. It was found that Cap mainly causes increase in K_ATPase value and to a lesser extent the decrease in V_max, which indicates that it is most likely a competitive inhibitor of actomyosin ATPase. Analysis of V_max and K_ATPase parameters in the presence of tropomyosin revealed that the latter is a noncompetitive inhibitor of the actomyosin ATPase.

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KEY WORDS: calponin-like protein, mussel, ATPase, V_max, K_ATPase, actomyosin, S1

DOI: 10.1134/S000629791601003X

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