Paracrystals, tropomyosin

Cohen, C., and Lonaley, W. (1996). Tropomyosin paracrystals formed by divalent crystals. Science 152, 794—796. 

The interaction of troponin T with tropomyosin was first shown by viscosity measurements of mixtures of the two components (Yamamoto and Maruyama, 1973) as well as by measurements of the electron microscopic density increase of specific regions in tropomyosin paracrystals or crystal nets (Greaser et al., 1973 Margossian and Cohen, 1973). 

When tropomyosin solutions are dialyzed against divalent cations such as Mg " or Ca +, fibrous paracrystals are formed. Paracrystalline tactoids under these conditions have a characteristic axial repeat period of 40 nm (Cohen and Longley, 1966). The axial periodicity is formed by the alternating arrangement of wide bright (27 nm) and narrow dark (13 nm) bands, each of which is surrounded by clear boundary lines. Two sets of oppositely directed tropomyosin filaments are arranged in the paracrystalline structure and each boundary line corresponds to the position of... 

Analysis of troponin-tropomyosin paracrystals clearly indicated that troponin, and consequently troponin T, is located around Cys-190, a... 

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