![]() ![]() Incorporation of the tropomyosin-troponin complex fully restored Ca2+ sensitivity without affecting maximum tension. In any case, the thin filaments of the cardiac contractile apparatus are considered to be assembled so as not to develop the highest degree of tension. As another possibility for augmented tension generation, we suggest the presence of an inhibitory system that was not reconstituted. The augmentation of tension was attributable to the elongation of reconstituted filaments. The active tension after the reconstitution of thin filaments reached 135 +/- 64% of the original level. By incorporating exogenous actin into these thin filament-free fibers, actin filaments were reconstituted, and active tension, which was insensitive to Ca2+, was restored. Under these conditions no active tension could be generated. First, all thin filaments other than short fragments at the Z line were removed by treatment with gelsolin. In this study we have achieved the structural and functional reconstitution of thin filaments in the cardiac contractile apparatus. In addition, this approach is a powerful technique for examining the structure and function of a specific component of the contractile system. Selective removal and reconstitution of the components are useful means of examining this mechanism. The molecular mechanism underlying the formation of this apparatus remains, however, to be elucidated. ![]() The muscle contractile apparatus has a highly ordered liquid crystalline structure. ![]() The prediction tool which developed in this work was incorporated in the SOSUIcoil system which predicts the coiled coil regions. Thus, the dynamic changes in the structure of the coiled coils around the fragile points may be related to the biological functions of the proteins. In contrast, the fluctuations in the hydrophobic outfield regions were reduced, suggesting a structural change of the coiled coils to balance these regions. Next, we examined the enhanced fluctuation around these predicted fragile points using the B-factor for the three dimensional structure of coiled coil proteins from the SCOP database and found that the fluctuations in the hydrophilic core regions were significantly larger than those in the regions of the normal coiled coil. The results of AFM imaging showed four main flexible regions in a single myosin rod and of the 17 possible fragile points predicted, 16 were located in the four experimental bending regions. Here, we investigated the myosin rods using this prediction system. The prediction system comprises two modules: identification of heptad break points and prediction of fragile points in the coiled coil due to the hydrophilic core or hydrophobic outfield region. A prediction system for identifying the region of flexible regions of the coiled coil was developed to determine the bending positions of the myosin rods using atomic force microscopy (AFM) and to analyze the molecular structures of proteins containing coiled coils. ![]()
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