Crystal structure of the protein histidine phosphatase SixA in the multistep His-Asp phosphorelay
Crystal structure of the protein histidine phosphatase SixA in the multistep His-Asp phosphorelay
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DOI：
10.1111/j.1365-2443.2005.00817.x
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发表时间：
2005-01-01
期刊：
影响因子：
2.1
通讯作者：
Hakoshima, T
中科院分区：
文献类型：
--
作者：
Hamada, K;Kato, M;Hakoshima, T
多重组氨酸-天冬氨酸磷酸中继系统在微生物和植物的细胞适应环境中发挥着至关重要的作用。与高等真核生物中的激酶磷酸酶系统一样，多个步骤为磷酸酶提供了额外的调节检查点。大肠杆菌磷酸酶 SixA 对位于参与厌氧反应的组氨酸激酶 ArcB C 末端的含组氨酸磷酸转移 (HPt) 结构域表现出蛋白磷酸酶活性。我们分别以 2.06 埃和 1.90 埃的分辨率确定了 SixA 的游离形式和钨酸盐结合形式的晶体结构。结果提供了细菌蛋白组氨酸磷酸酶的第一个三维视图，揭示了与活性位点含有精氨酸-组氨酸-甘氨酸（RHG）基序的磷酸酶家族相关的紧凑的α/β结构。与这些 RHG 磷酸酶相比，SixA 缺乏额外的 α 螺旋子结构域作为活性位点上的盖子，从而形成相对较浅的凹槽，对于容纳 ArcB 的 HPt 结构域非常重要。模拟底物磷酸基团的钨酸根离子位于活性位点的中心，其中活性残基 His8 以串联亲核攻击的方式指向钨原子。
The multiple histidine-aspartate phosphorelay system plays a crucial role in cellular adaptation to environments in microorganisms and plants. Like kinase-phosphatase systems in higher eukaryotes, the multiple steps provide additional regulatory checkpoints with phosphatases. The Escherichia coli phosphatase SixA exhibits protein phosphatase activity against the histidine-containing phosphotransfer (HPt) domain located in the C-terminus of the histidine kinase ArcB engaged in anaerobic responses. We have determined the crystal structures of the free and tungstate-bound forms of SixA at 2.06 Angstrom and 1.90 Angstrom resolution, respectively. The results provide the first three-dimensional view of a bacterial protein histidine phosphatase, revealing a compact alpha/beta architecture related to a family of phosphatases containing the arginine-histidine-glycine (RHG) motif at their active sites. Compared with these RHG phosphatases, SixA lacks an extra alpha-helical subdomain as a lid over the active site, thereby forming a relatively shallow groove important for the accommodation of the HPt domain of ArcB. The tungstate ion, which mimics the substrate phosphate group, is located at the centre of the active site where the active residue, His8, points to the tungsten atom in the mode of in-line nucleophilic attack.