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

V. V. Sirenko1, A. V. Dobrzhanskaya2, N. S. Shelud’ko2, and Y. S. Borovikov1*

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
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 Vmax and KATPase 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 KATPase value and to a lesser extent the decrease in Vmax, which indicates that it is most likely a competitive inhibitor of actomyosin ATPase. Analysis of Vmax and KATPase parameters in the presence of tropomyosin revealed that the latter is a noncompetitive inhibitor of the actomyosin ATPase.
KEY WORDS: calponin-like protein, mussel, ATPase, Vmax, KATPase, actomyosin, S1

DOI: 10.1134/S000629791601003X