Role of the D-Loops in Allosteric Control of ATP Hydrolysis in an ABC Transporter
Role of the D-Loops in Allosteric Control of ATP Hydrolysis in an ABC Transporter
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DOI：
10.1021/jp211139s
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发表时间：
2012-03-22
影响因子：
2.9
通讯作者：
George, Anthony M.
中科院分区：
文献类型：
--
作者：
Jones, Peter M.;George, Anthony M.
ABC转运蛋白将ATP水解与底物跨细胞膜的移动偶联。它们包含两个跨膜结构域和两个胞质核苷酸结合结构域，形成两个协同水解ATP的活性位点。ATP水解的机制是有争议的，其变构控制的结构动力学基础未知。在这里，我们报告的ATP/载脂蛋白和ATP/ADP状态的细菌ABC出口商Sav 1866，其中蛋白质的细胞质区域在明确的水模拟150 ns的分子动力学模拟。在ATP/载脂蛋白状态的模拟中，我们观察到，第一次，构象的活性位点与典型的几何形状的一个在线亲核攻击的ATP γ-磷酸。紧邻步行者B基序下游的保守谷氨酸是催化碱基，与H环组氨酸形成二联体，而Q环谷氨酰胺具有组织作用。每个D-环提供了一个协调残基的攻击水，并与模拟的ATP/ADP状态的比较表明，通过其灵活性，D-环调节形成的水解能力状态。一个涉及偶联螺旋的全局开关描绘了ABC转运蛋白中ATP水解的变构控制介导的信号传递途径。
ABC transporters couple ATP hydrolysis to movement of substrates across cell membranes. They comprise two transmembrane domains and two cytosolic nucleotide-binding domains forming two active sites that hydrolyze ATP cooperatively. The mechanism of ATP hydrolysis is controversial and the structural dynamic basis of its allosteric control unknown. Here we report molecular dynamics simulations of the ATP/apo and ATP/ADP states of the bacterial ABC exporter Sav1866, in which the cytoplasmic region of the protein was simulated in explicit water for 150 ns. In the simulation of the ATP/apo state, we observed, for the first time, conformers of the active site with the canonical geometry for an in-line nucleophilic attack on the ATP gamma-phosphate. The conserved glutamate immediately downstream of the Walker B motif is the catalytic base, forming a dyad with the H-loop histidine, whereas the Q-loop glutamine has an organizing role. Each D-loop provides a coordinating residue of the attacking water, and comparison with the simulation of the ATP/ADP state suggests that via their flexibility, the D-loops modulate formation of the hydrolysis-competent state. A global switch involving a coupling helix delineates the signal transmission route by which allosteric control of ATP hydrolysis in ABC transporters is mediated.