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首页> 外文期刊>Biochemistry >Push and Pull of Tropomyosin’s Opposite Effects on Myosin Attachment to Actin. A Chimeric Tropomyosin Host−Guest Study
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Push and Pull of Tropomyosin’s Opposite Effects on Myosin Attachment to Actin. A Chimeric Tropomyosin Host−Guest Study

机译：推力和推力肌红蛋白对肌球蛋白与肌动蛋白的附着作用相反。嵌合的Tropomyosin宿主-来宾研究

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摘要

Tropomyosin is a ubiquitous actin-binding protein with an extended coiled-coil structure.nTropomyosin-actin interactions are weak and loosely specific, but they potently influence myosin. Onensuch influence is inhibitory and is due to tropomyosin’s statistically preferred positions on actin that stericallyninterfere with actin’s strong attachment site for myosin. Contrastingly, tropomyosin’s other influence isnactivating. It increases myosin’s overall actin affinity ∼4-fold. Stoichiometric considerations cause thisnactivating effect to equate to an ∼47n-fold effect ofmyosin on the actin affinity of tropomyosin. These positive,nmutual, myosin-tropomyosin effects are absent if Saccharomyces cerevisiae tropomyosin replaces mamma-nlian tropomyosin. To investigate these phenomena, chimeric tropomyosins were generated in whichn38-residue muscle tropomyosin segments replaced a natural duplication within S. cerevisiae tropomyosin TPM1.nTwo such chimeric tropomyosins were sufficiently folded coiled coils to allow functional study. The twonchimeras differed from TPM1 but in opposite ways. Consistent with steric interference, myosin greatlyndecreased the actin affinity of chimera 7, which contained muscle tropomyosin residues 228-265. On thenother hand, myosin S1 increased by an order of magnitude the actin affinity of chimera 3, which containednmuscle tropomyosin residues 74-111. Similarly,myosin S1-ADP binding to actinwas strengthened 2-fold bynsubstitution of chimera 3 tropomyosin for wild-type TPM1. Thus, a yeast tropomyosin was induced to mimicnthe activating behavior of mammalian tropomyosin by inserting a mammalian tropomyosin sequence. Thendata were not consistent with direct tropomyosin-myosin binding. Rather, they suggest an allostericnmechanism, in which myosin and tropomyosin share an effect on the actin filament.
机译：Tropomyosin是一种普遍存在的肌动蛋白结合蛋白，具有扩展的卷曲螺旋结构。nTropomyosin-actin相互作用较弱且特异性较弱，但会强烈影响肌球蛋白。产生这种影响是有抑制作用的，这是由于原肌球蛋白在肌动蛋白上的统计学上偏爱的位置在空间上干扰了肌动蛋白对肌球蛋白的牢固附着位点。相反，原肌球蛋白的其他影响却没有激活。它使肌球蛋白的整体肌动蛋白亲和力增加约4倍。从化学计量上考虑，这种激活作用相当于肌球蛋白对原肌球蛋白肌动蛋白亲和力的约47n倍作用。如果啤酒酵母原肌球蛋白替代了哺乳动物的原肌球蛋白，则这些阳性的，相互的，肌球蛋白原肌球蛋白将不存在。为了研究这些现象，产生了嵌合原肌球蛋白，其中38个残基肌原肌球蛋白片段取代了酿酒酵母原肌球蛋白TPM1内的自然复制。n两种这样的嵌合原肌球蛋白被充分折叠的卷曲螺旋以进行功能研究。 twonchimeras与TPM1不同，但方向相反。与空间干扰一致，肌球蛋白大大降低了嵌合体7的肌动蛋白亲和力，其中包含肌肉原肌球蛋白残基228-265。另一方面，肌球蛋白S1使嵌合体3的肌动蛋白亲和力增加一个数量级，所述嵌合体3包含肌原肌球蛋白残基74-111。同样，肌球蛋白S1-ADP与肌动蛋白的结合被嵌合体3原肌球蛋白对野生型TPM1的2倍取代。因此，通过插入哺乳动物原肌球蛋白序列，诱导酵母原肌球蛋白模拟哺乳动物原肌球蛋白的活化行为。然后数据与原肌球蛋白-肌球蛋白直接结合不一致。相反，他们提出了一种变构机制，其中肌球蛋白和原肌球蛋白共享肌动蛋白丝的作用。

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  • 来源
    《Biochemistry》 |2010年第51期|p.10873-10880|共8页
  • 作者

    Laith F. Ali Joshua M. Cohen and Larry S. Tobacman;

  • 作者单位

    ‡Departments of Medicine,§Physiology and Biophysics, and University of Illinois at Chicago,Chicago, Illinois 60612, United States;

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