Lehrer S S, Morris E P
J Biol Chem. 1984 Feb 25;259(4):2070-2.
Chicken gizzard tropomyosin, like rabbit skeletal tropomyosin, inhibits and activates skeletal actomyosin subfragment 1 ATPase at low and high [subfragment 1], respectively, showing that both smooth and skeletal tropomyosin qualitatively produce similar cooperative effects on activity. For gizzard tropomyosin, however, the extent of the inhibition was less, and the activation curve rose more sharply at lower [subfragment 1]. In terms of a two-state cooperative activity model for the actin-tropomyosin filament (Hill, T. L., Eisenberg, E., and Chalovich, J. (1981) Biophys. J. 35, 99-112), these results qualitatively suggest that, for the gizzard tropomyosin system, more units are initially in the active state (in the absence of subfragment 1) and that the switching of units to the active state is more cooperative. The greater cooperativity indicated for the gizzard system may be a consequence of the greater rigidity of gizzard tropomyosin indicated from conformational studies.
鸡胗原肌球蛋白与兔骨骼肌原肌球蛋白一样，分别在低和高[亚片段1]浓度时抑制和激活骨骼肌肌动球蛋白亚片段1的ATP酶，这表明平滑肌和骨骼肌原肌球蛋白在性质上对活性产生相似的协同效应。然而，对于鸡胗原肌球蛋白，抑制程度较小，并且在较低[亚片段1]浓度时激活曲线上升更陡峭。根据肌动蛋白-原肌球蛋白丝的双态协同活性模型（希尔，T.L.，艾森伯格，E.，和查洛维奇，J.（1981年）《生物物理学杂志》35卷，99 - 112页），这些结果定性地表明，对于鸡胗原肌球蛋白系统，更多的单元最初处于活性状态（在没有亚片段1的情况下），并且单元向活性状态的转变更具协同性。鸡胗系统所显示的更大协同性可能是构象研究表明的鸡胗原肌球蛋白更大刚性的结果。
