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首页> 外文期刊>Protein Science: A Publication of the Protein Society >Fine-tuning function: correlation of hinge domain interactions with functional distinctions between LacI and PurR.
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Fine-tuning function: correlation of hinge domain interactions with functional distinctions between LacI and PurR.

机译:微调功能:铰链域相互作用与LacI和PurR之间的功能区别的相关性。

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摘要

LacI and PurR are highly homologous proteins. Their functional units are homodimers, with an N-terminal DNA binding domain that comprises the helix-turn-helix (HTH), N-linker, and hinge regions from both monomers. Hinge structural changes are known to occur upon DNA dissociation but are difficult to monitor experimentally. The initial steps of hinge unfolding were therefore examined using molecular dynamics simulations, utilizing a truncated, chimeric protein comprising the LacI HTH/N-linker and PurR hinge. A terminal Gly-Cys-Gly was added to allow "dimerization" through disulfide bond formation. Simulations indicate that differences in LacI and PurR hinge primary sequence affect the quaternary structure of the hinge x hinge' interface. However, these alternate hinge orientations would be sterically restricted by the core domain. These results prompted detailed comparison of recently available DNA-bound structures for LacI and truncated LacI(1-62) with the PurR structure. Examination revealed that different N-linker and hinge contacts to the core domain of the partner monomer (which binds effector molecule) affect the juxtapositions of the HTH, N-linker, and hinge regions in the DNA binding domain. In addition, the two full-length repressors exhibit significant differences in the interactions between the core and the C-linker connection to the DNA binding domain. Both linkers and the hinge have been implicated in the allosteric response of these repressors. Intriguingly, one functional difference between these two proteins is that they exhibit opposite allosteric response to effector. Simulations and observed structural distinctions are correlated with mutational analysis and sequence information from the LacI/GalR family to formulate a mechanism for fine-tuning individual repressor function.
机译:LacI和PurR是高度同源的蛋白质。它们的功能单元是同型二聚体,具有一个N端DNA结合结构域,该结构域包含两个单体的螺旋-转-螺旋(HTH),N-接头和铰链区。已知在DNA解离时会发生铰链结构变化,但是很难通过实验监测。因此,使用分子动力学模拟,使用包含LacI HTH / N-接头和PurR铰链的截短的嵌合蛋白,检查了铰链展开的初始步骤。添加末端Gly-Cys-Gly以通过二硫键形成而进行“二聚”。仿真表明,LacI和PurR铰链一级序列的差异会影响铰链x铰链接口的四级结构。但是,这些替代的铰链方向在空间上会受到核心区域的限制。这些结果促使详细比较最近可用的DNA结合的LacI和带有PurR结构的截短的LacI(1-62)的DNA。检查表明,与伴侣单体(结合效应分子)的核心结构域的不同N接头和铰链接触会影响HTH,N接头和铰链区域在DNA结合结构域中的并列。另外,两个全长阻遏物在核心和与DNA结合结构域的C-接头连接之间的相互作用中表现出显着差异。连接子和铰链都与这些阻遏物的变构反应有关。有趣的是,这两种蛋白质之间的功能差异是它们对效应子表现出相反的变构反应。模拟和观察到的结构差异与来自LacI / GalR家族的突变分析和序列信息相关,以建立微调单个阻遏物功能的机制。

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