title: Troponin-like regulation in muscle thin filaments of the mussel Crenomytilus grayanus (Bivalvia: Mytiloida).
abstract: Muscles of bivalve molluscs have double calcium regulation--myosin-linked and actin-linked. While the mechanism of myosin-linked regulation is sufficiently studied, there is still no consensus on the mechanism of actin-linked regulation. Earlier we showed a high degree of Ca2+-sensitivity of thin filaments from the adductor muscle of the mussel Crenomytilus grayanus (Mytiloida). In order to elucidate the nature of this regulation, we isolated the fraction of minor proteins from the mussel thin filaments, which confers Ca2+-sensitivity to reconstituted actomyosin-tropomyosin. Proteins of this fraction, ABP-19, ABP-20, and ABP-28, were chromatographically purified and identified. According to the results of mass spectrometry and Western blot analysis, as well as by their functional properties, these mussel actin-binding proteins appeared to correspond to the troponin components from the skeletal muscles of vertebrates (TnC, TnI and TnT). The reconstituted mussel troponin complex confers to actomyosin-tropomyosin more than 80% Ca2+-sensitivity. The in vivo molar ratio of actin/tropomyosin/troponin was calculated to be 7:1:0.5, i.e., the content of troponin in mussel thin filaments is two times lower than in thin filaments of skeletal muscles of vertebrates. These data demonstrate that troponin-like regulation found in the catch muscle of the mussel C. grayanus is present at least in two suborders of bivalves: Pectinoida and Mytiloida.
authors.affiliation: Laboratory of Cell Biophysics, A.V. Zhirmunsky Institute of Marine Biology, Far East Branch of Russian Academy of Sciences, 17, Palchevsky St., 690041 Vladivostok, Russia. Electronic address: vyatchin@live.ru.
authors.forename: Ilya G
authors.initials: IG
authors.lastname: Vyatchin
authors.affiliation: Laboratory of Cell Biophysics, A.V. Zhirmunsky Institute of Marine Biology, Far East Branch of Russian Academy of Sciences, 17, Palchevsky St., 690041 Vladivostok, Russia.
authors.forename: Ulyana V
authors.initials: UV
authors.lastname: Shevchenko
authors.affiliation: Laboratory of Cell Biophysics, A.V. Zhirmunsky Institute of Marine Biology, Far East Branch of Russian Academy of Sciences, 17, Palchevsky St., 690041 Vladivostok, Russia.
authors.forename: Stanislav S
authors.initials: SS
authors.lastname: Lazarev
authors.affiliation: Laboratory of Cell Biophysics, A.V. Zhirmunsky Institute of Marine Biology, Far East Branch of Russian Academy of Sciences, 17, Palchevsky St., 690041 Vladivostok, Russia.
authors.forename: Oleg S
authors.initials: OS
authors.lastname: Matusovsky
authors.affiliation: Laboratory of Cell Biophysics, A.V. Zhirmunsky Institute of Marine Biology, Far East Branch of Russian Academy of Sciences, 17, Palchevsky St., 690041 Vladivostok, Russia.
authors.forename: Nikolay S
authors.initials: NS
authors.lastname: Shelud'ko
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000205:Actomyosin / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002148:Calmodulin-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D009210:Myofibrils / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D009218:Myosins / Q000235:genetics / Q000378:metabolism; D049879:Mytilidae / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011817:Rabbits; D016415:Sequence Alignment; D014335:Tropomyosin / Q000235:genetics / Q000378:metabolism*; D014336:Troponin / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D002148:Calmodulin-Binding Proteins; D014335:Tropomyosin; D014336:Troponin; D000205:Actomyosin; D009218:Myosins; D002118:Calcium
keywords: Bivalve catch muscle; Ca(2+)-regulation; Caldesmon; Thin filaments; Tropomyosin; Troponin