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首页> 美国卫生研究院文献>PLoS Clinical Trials >Dramatic Structural Changes Resulting from the Loss of a Crucial Hydrogen Bond in the Hinge Region Involved in C-Terminal Helix Swapping in SurE: A Survival Protein from Salmonella typhimurium
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Dramatic Structural Changes Resulting from the Loss of a Crucial Hydrogen Bond in the Hinge Region Involved in C-Terminal Helix Swapping in SurE: A Survival Protein from Salmonella typhimurium

机译：戏剧性的结构变化，由于参与SurE的C末端螺旋交换的铰链区域中一个重要氢键的丧失而引起：鼠伤寒沙门氏菌的生存蛋白

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摘要

Domain swapping is an interesting feature of some oligomeric proteins in which each protomer of the oligomer provides an identical surface for exclusive interaction with a segment or domain belonging to another protomer. Here we report results of mutagenesis experiments on the structure of C-terminal helix swapped dimer of a stationary phase survival protein from Salmonella typhimurium (StSurE). Wild type StSurE is a dimer in which a large helical segment at the C-terminus and a tetramerization loop comprising two β strands are swapped between the protomers. Key residues in StSurE that might promote C-terminal helix swapping were identified by sequence and structural comparisons. Three mutants in which the helix swapping is likely to be avoided were constructed and expressed in E. coli. Three-dimensional X-ray crystal structures of the mutants H234A and D230A/H234A could be determined at 2.1 Å and 2.35 Å resolutions, respectively. Contrary to expectations, helix swapping was mostly retained in both the mutants. The loss of the crucial D230 OD2– H234 NE2 hydrogen bond (2.89 Å in the wild type structure) in the hinge region was compensated by new inter and intra-chain interactions. However, the two fold molecular symmetry was lost and there were large conformational changes throughout the polypeptide. In spite of these changes, the dimeric structure and an approximate tetrameric organization were retained, probably due to the interactions involving the tetramerization loop. Mutants were mostly functionally inactive, highlighting the importance of precise inter-subunit interactions for the symmetry and function of StSurE.
机译：域交换是某些寡聚蛋白的一个有趣特征，其中每个寡聚物的protomer提供一个相同的表面，用于与属于另一个protomer的区段或结构域进行排他性相互作用。在这里，我们报道了鼠伤寒沙门氏菌（StSurE）固定相存活蛋白的C末端螺旋交换二聚体结构的诱变实验结果。野生型StSurE是一个二聚体，其中在C端之间有一个大的螺旋节段和一个包含两条β链的四聚环，在原形体之间交换。通过序列和结构比较，确定了可能促进C末端螺旋交换的StSurE中的关键残基。在大肠杆菌中构建并表达了可能避免螺旋交换的三个突变体。突变体H234A和D230A / H234A的三维X射线晶体结构可以分别以2.1Å和2.35Å的分辨率确定。与预期相反，两个突变体中大多数都保留了螺旋交换。关键的D230 OD2-H234 NE2氢键（在野生型结构中为2.89Å）的丢失在链区和链内的新相互作用得到了补偿。然而，失去了两倍的分子对称性，并且整个多肽中存在大的构象变化。尽管有这些变化，可能由于涉及四聚环的相互作用而保留了二聚体结构和近似的四聚体组织。突变体大部分在功能上不活跃，突显了精确的亚基间相互作用对于StSurE对称性和功能的重要性。

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