Critical Role of Water Molecules in Proton Translocation by the Membrane-Bound Transhydrogenase
Critical Role of Water Molecules in Proton Translocation by the Membrane-Bound Transhydrogenase
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DOI：
10.1016/j.str.2017.05.022
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发表时间：
2017-07-05
期刊：
影响因子：
5.7
通讯作者：
Zhang, Qinghai
中科院分区：
文献类型：
--
作者：
Padayatti, Pius S.;Leung, Josephine H.;Zhang, Qinghai
烟酰胺核苷酸转氢酶（TH）是一种完整的膜酶，在细菌和真核生物中利用质子动力驱动氢化物从NADH转移到NADP（+）。在这里，我们解决了2.2埃晶体结构的TH跨膜结构域（嗜热栖热菌）在pH 6.5。这种结构表现出构象变化的螺旋位置从以前的结构解决在pH 8.5，并揭示内部水分子与残基相互作用涉及质子易位。与分子动力学模拟一起，我们表明，瞬态水流过一个狭窄的孔和疏水性的“干”区域中的膜通道的中间，与关键残基His42（α 2）（链A）被质子化和Thr214（β）（链B）显示构象变化，分别门通道访问细胞质和周质室。Thr214（β）突变为Ala使酶失活。这些数据提供了新的见解TH质子易位的门控机制。
The nicotinamide nucleotide transhydrogenase (TH) is an integral membrane enzyme that uses the proton-motive force to drive hydride transfer from NADH to NADP(+) in bacteria and eukaryotes. Here we solved a 2.2-angstrom crystal structure of the TH transmembrane domain (Thermus thermophilus) at pH 6.5. This structure exhibits conformational changes of helix positions from a previous structure solved at pH 8.5, and reveals internal water molecules interacting with residues implicated in proton translocation. Together with molecular dynamics simulations, we show that transient water flows across a narrow pore and a hydrophobic "dry'' region in the middle of the membrane channel, with key residues His42(alpha 2) (chain A) being protonated and Thr214(beta) (chain B) displaying a conformational change, respectively, to gate the channel access to both cytoplasmic and periplasmic chambers. Mutation of Thr214(beta) to Ala deactivated the enzyme. These data provide new insights into the gating mechanism of proton translocation in TH.