REFINED STRUCTURES OF THE LIGAND-BINDING DOMAIN OF THE ASPARTATE RECEPTOR FROM SALMONELLA-TYPHIMURIUM
REFINED STRUCTURES OF THE LIGAND-BINDING DOMAIN OF THE ASPARTATE RECEPTOR FROM SALMONELLA-TYPHIMURIUM
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DOI：
10.1006/jmbi.1993.1411
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发表时间：
1993-07-20
影响因子：
5.6
通讯作者：
KIM, SH
中科院分区：
文献类型：
--
作者：
SCOTT, WG;MILLIGAN, DL;KIM, SH
天冬氨酸受体是一种跨膜信号蛋白，介导细菌的趋化行为。鼠伤寒沙门氏菌和大肠杆菌中的天冬氨酸受体在有无天冬氨酸的情况下都以两个亚单位的二聚体的形式存在。我们以前已经报道了THs的外部配体结合域的三维结构。结合和不结合天冬氨酸的鼠伤寒沙门冬氨酸受体。天冬氨酸受体的外部或周质区域是一个由四个α螺旋束亚基组成的二聚体；单个天冬氨酸分子与位于亚基界面的两个位点中的一个结合，增加了亚基之间的亲和力。两个相关亚基之间的二聚体界面主要由每个四α-螺旋束亚基的N-末端螺旋的侧链介导的接触组成。我们将天冬氨酸受体的配体结合域结构，在存在和不存在结合芳香族化合物的情况下，分别细化到2·2？和2？3？分辨率，以及在Au(I)、Hg(II)和铂(IV)络合离子存在时，分别以2？4？、3？0？和3？3？的分辨率计算晶体结构。讨论了芳香族配体结合部位和金属离子结合部位可能的生物学相关性。四个α-螺旋束亚基的二聚体组成了THs的周质区域。鼠伤寒杆菌天冬氨酸受体为理解对相关趋化跨膜受体进行突变分析的结果提供了基础。晶体结构分析为你的突变提供了一种解释。大肠天冬氨酸受体影响其与周质麦芽糖结合蛋白的结合，以及如何在较远的亲缘关系中发生突变。ColiTrg趋化受体影响其与周质核糖和葡萄糖-半乳糖结合蛋白的结合。
The aspartate receptor is a transmembrane signalling protein that mediates chemotaxis behaviour in bacteria. Aspartate receptors inSalmonella typhimuriumandEscherichia coliexist as dimers of two subunits in the presence as well as in the absence of aspartate. We have previously reported the three-dimensional structures of the external ligand-binding domain of theS. typhimuriumaspartate receptor with and without bound aspartate. The external or periplasmic region of the aspartate receptor is a dimer of four-α-helical bundle subunits; a single aspartate molecule binds to one of two sites residing at the subunit interface, increasing the affinity of the subunits for one another.Here we report the results of a detailed analysis of the aspartate receptor ligand-binding domain structure (residues 25 to 188). The dimer interface between the twofold related subunits consists primarily of contacts mediated by the side-chains of the N-terminal helix of each four-α-helical bundle subunit. The N-terminal helices pack approximately 20° from parallel as an approximate coiled-coil super-secondary structure.We have refined aspartate receptor ligand-binding domain structures in the presence and in the absence of a bound aromatic compound, 1,10-phenanthroline, to 2·2 Å and 2·3 Å resolution, respectively, as well as crystal structures in the presence of specifically bound Au(I), Hg(II) and Pt(IV) complex ions at 2·4 Å, 3·0 Å and 3·3 Å resolution, respectively. The possible biological relevance of the aromatic ligand-binding site and the metal ion-binding sites is discussed.The dimer of four-α-helical bundle subunits composing the periplasmic region of theS. typhimuriumaspartate receptor provides a basis for understanding the results of mutational analyses performed on related chemotaxis transmembrane receptors. The crystal structure analysis provides an explanation for the way in which mutations in theE. coliaspartate receptor affect its binding to the periplasmic maltose-binding protein and how mutations in the more distantly relatedE. coliTrg chemotaxis receptor affect its binding to the periplasmic ribose and glucose-galactose binding proteins.