[Modulation of S-1 conformation and inhibition of the skeletal muscle S-1-ATPase by calponin of the mussel].

A novel 40 kDa protein has been detected in native thin filaments from catch muscles of the mussel Crenomytilus grayanus. In this study, using skeletal muscle actin and S-1, we investigated the effects of the mussel 40-kDa actin-binding protein on the acto · S-1 ATPase activity. On increasing the 40-kDa actin-binding protein (CaP-40) concentration, the actin-activated ATPase activity decreased, and was inhibited 80% at a CaP-40 to actin ratio of 0.

[Abnormal tropomyosin function in ATPase cycle in hypertrophic and dilated cardiomyopathies].

Pathogenesis of most myopathies including inherited hypertrophic (HCM) and dilated (DCM) cardiomyopathies is based on modification of structural state of contractile proteins induced by point mutations, such as mutations in alpha-tropomyosin (TM). To understand the mechanism of abnormal function of contractile system of muscle fiber due to Glu180Gly, Asp175 or Glu40Lys, Glu54Lys mutations in alpha-TM associated with HCM or DCM, we specifically labeled alpha-TM by fluorescence probe 5-IAF after Cys-190 and examined the position and mobility of the IAF-TM in the ATP hydrolysis cycle using polarized fluorescence technique. Analysis of the data suggested that the point mutations in alpha-TM associated with hypertrophic or dilated cardiomyopathy caused abnormal changes in the affinity ofTM to actin and in the position of this protein on the thin filaments in the ATPase cycle.

[Hyperthyreosis inhibits the ability of actin to form strong-binding with myosin].

The effect of hyperthyreosis development induced by the increase in thyroid hormones in rats (during 2-4 weeks) on the orientation and mobility of fluorescent probe N-(iodoacetyl)-(1-naphtyl-5-sulpho-ethylenediamine) specifically bound to Cys 374 of actin in ghost muscle fibers isolated from fast (EDL) and slow (SOL) rat muscles was studied. It was found that the binding of myosin subfragment-1 (S1) to F-actin induced the typical for the formation of strong binding actomyosin decrease in mobility of actin subdomain 1 and its rotation towards thin filament periphery. Development of hyperthyreosis markedly inhibited these phenomena.

[Effect of hypothyreosis on actin subdomain-1 movement induced by myosin subfragment 1-binding in fast and slow rat skeletal muscles].

Orientation and mobility of fluorescent probe N-((iodoacetyl)-(1-naphtyl-5-sulpho-ethylenediamine)(1.5-IAEDANS)) specifically bound to Cys-374 of actin in ghost muscle fibers isolated from fast and slow rat muscles were studied by polarized fluorimetry in the absence and presence of myosin subfragment-1 (S1) in intact rats and in the animals with gradual (during 2-5 weeks) reduction of thyroid hormones synthesis (hypothyreosis development). S1 binding to F-actin of ghost muscle fibers was shown to induce changes in orientation of the dipoles of the fluorescent probe 1.

[The influence of caldesmon on strong binding of myosin with actin in denervated rat skeletal muscles].

The effect of caldesmon (CaD) on conformational changes in F-actin modified by fluorescent probe TRITC-phalloidin was investigated by polarized fluorimetry. Changes were induced by a subfragment-1 (S-1) of myosin in the absence or presence of CaD in ghost muscle fibers obtained from intact and denervated slow (SOL) and fast (EDL) skeletal muscles of rats. S-1 binding to actin of both SOL and EDL muscles was shown to cause changes in polarized parameters of TRITC-phalloidin typical for a strong actin-myosin binding as well as of transition ofactin subunits from "off" to "on" state.