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首页> 外文期刊>Biochemistry >The coil-to-helix transition in IlvN regulates the allosteric control of Escherichia coli acetohydroxyacid synthase i
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The coil-to-helix transition in IlvN regulates the allosteric control of Escherichia coli acetohydroxyacid synthase i

机译：IlvN中的线圈到螺旋过渡可调节大肠杆菌乙酰羟酸合酶i的变构控制

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摘要

The solution structure of IlvN, the regulatory subunit of Escherichia coli acetohydroxyacid synthase I, in the valine-bound form has been determined using high-resolution multidimensional, multinuclear nuclear magnetic resonance (NMR) methods. IlvN in the presence or absence of the effector molecule is present as a 22.5 kDa dimeric molecule. The ensemble of 20 low-energy structures shows a backbone root-mean-square deviation of 0.73 ± 0.13 ? and a root-mean-square deviation of 1.16 ± 0.13 ? for all heavy atoms. Furthermore, more than 98% of the backbone φ and ψ dihedral angles occupy the allowed and additionally allowed regions of the Ramachandran map, which is indicative of the fact that the structures are of high stereochemical quality. Each protomer exhibits a βαββαβα topology that is a characteristic feature of the ACT domain seen in metabolic enzymes. In the valine-bound form, IlvN exists apparently as a single conformer. In the free form, IlvN exists as a mixture of conformational states that are in intermediate exchange on the NMR time scale. Thus, a large shift in the conformational equilibrium is observed upon going from the free form to the bound form. The structure of the valine-bound form of IlvN was found to be similar to that of the ACT domain of the unliganded form of IlvH. Comparisons of the structures of the unliganded forms of these proteins suggest significant differences. The structural and conformational properties of IlvN determined here have allowed a better understanding of the mechanism of regulation of branched chain amino acid biosynthesis.
机译：已使用高分辨率多维，多核核磁共振（NMR）方法确定了缬氨酸结合形式的大肠杆菌乙酰羟酸合酶I的调节亚基IlvN的溶液结构。在存在或不存在效应子分子的情况下，IlvN以22.5 kDa二聚体分子的形式存在。 20个低能量结构的集合显示主干的均方根偏差为0.73±0.13？均方根偏差为1.16±0.13？对于所有重原子。此外，超过98％的骨架φ和ψ二面角占据了Ramachandran图的允许区域和附加允许区域，这表明该结构具有较高的立体化学质量。每个启动子都具有一个βαββαβα拓扑结构，这是在代谢酶中看到的ACT域的特征。以缬氨酸结合的形式，IlvN显然以单个构象体存在。在游离形式中，IlvN以构象状态的混合物形式存在，在NMR时间尺度上处于中间交换状态。因此，在从自由形式转变为结合形式时，观察到构象平衡发生了大的变化。发现IlvN的缬氨酸结合形式的结构与IlvH的非配体形式的ACT结构域的结构相似。这些蛋白质的非配体形式的结构比较表明存在显着差异。此处确定的IlvN的结构和构象性质使人们对支链氨基酸生物合成的调节机制有了更好的了解。

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