The active state of the thin filament is destabilized by an internal deletion in tropomyosin
The active state of the thin filament is destabilized by an internal deletion in tropomyosin
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DOI：
10.1074/jbc.272.22.14051
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发表时间：
1997-05-30
影响因子：
4.8
通讯作者：
Tobacman, LS
中科院分区：
文献类型：
--
作者：
Landis, CA;Bobkova, A;Tobacman, LS
通过从骨骼肌α-原肌球蛋白中删除第49-167位的内部残基，研究了原肌球蛋白的三个连续准等效区的功能。这种缺失突变体原肌球蛋白跨越四个而不是正常的七个肌动蛋白，并且大多数被认为与肌钙蛋白相互作用的原肌球蛋白区在突变体中被保留并且不间断。将突变原肌球蛋白与经修饰以在功能上类似于肌肉原肌球蛋白的全长对照分子进行比较（Monteiro，P. B.，拉塔罗河C.的方法，Ferro，J. A.，和Reinach，F. C.（1994）J.Biol.Chem.269，10461-10466）。原肌球蛋白缺失抑制肌动蛋白-肌球蛋白亚片段1 MgATPase速率和在体外滑动的细丝在重的肌球蛋白包被的表面，这种抑制不逆转肌钙蛋白加Ca 2+。类似的原肌球蛋白对肌动蛋白的亲和力，无论删除，表明删除的区域在没有其他蛋白质的情况下与肌动蛋白几乎没有相互作用。同样，删除也没有削弱肌钙蛋白-原肌球蛋白复合物与肌动蛋白的结合。此外，钙离子对肌钙蛋白-原肌球蛋白对肌动蛋白的亲和力有2倍的影响，无论删除，值得注意的是，删除大大削弱了原肌球蛋白与肌球蛋白亚片段1-修饰的肌动蛋白的结合，全长原肌球蛋白具有100倍的亲和力，从删除产生的抑制特性归因于肌球蛋白诱导的活性状态的细丝的缺陷稳定。
The function of three of tropomyosin's sequential quasiequivalent regions was studied by deletion from skeletal muscle alpha-tropomyosin of internal residues 49-167, This deletion mutant tropomyosin spans four instead of the normal seven actins, and most of the tropomyosin region believed to interact with troponin is retained and uninterrupted in the mutant. The mutant tropomyosin was compared with a full-length control molecule that was modified to functionally resemble muscle tropomyosin (Monteiro, P. B., Lataro, R. C., Ferro, J. A., and Reinach, F. C. (1994) J. Biol. Chem. 269, 10461-10466). The tropomyosin deletion suppressed the actin-myosin subfragment 1 MgATPase rate and the in vitro sliding of thin filaments over a heavy meromyosin-coated surface, This inhibition was not reversed by troponin plus Ca2+. Comparable tropomyosin affinities for actin, regardless of the deletion, suggest that the deleted region has little interaction with actin in the absence of other proteins, Similarly, the deletion did not weaken binding of the troponin-tropomyosin complex to actin. Furthermore, Ca2+ had a 2-fold effect on troponin-tropomyosin's affinity for actin, regardless of the deletion, Notably, the deletion greatly weakened tropomyosin binding to myosin subfragment 1-decorated actin, with the full-length tropomyosin having a 100-fold greater affinity, The inhibitory properties resulting from the deletion are attributed to defective stabilization of the myosin-induced active state of the thin filament.