Bound water in the proton translocation mechanism of the haem‐copper oxidases
Bound water in the proton translocation mechanism of the haem‐copper oxidases
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血红素铜氧化酶质子易位机制中的结合水
DOI：
10.1016/s0014-5793(97)01003-x
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发表时间：
1997
期刊：
影响因子：
3.5
通讯作者：
Mårten Wikström
中科院分区：
文献类型：
--
作者：
S. Riistama;Gerhard Hummer;A. Puustinen;A. Puustinen;R. Dyer;William H. Woodruff;Mårten Wikström
我们探讨了血红素铜氧化酶移位质子的分子机制。 O2 还原成水发生在血红素铁铜 (CuB) 中心，质子从膜的一侧通过酶中的“通道”结构进入。统计力学计算预测了该通道内的结合水分子，而诱变实验表明，打破这种水结构会阻碍质子易位。氢键水分子通过保守的谷氨酸残基进一步将通道连接到 CuB 的组氨酸配体。谷氨酸侧链在质子转移过程中可能必须移动，因为如果被迫与附近的赖氨酸或精氨酸相互作用，质子易位就会被取消。扰动 CuBligand 结构会改变红外模式，这可能归因于结合水的 OH 延伸。它对谷氨酸的突变敏感，支持其与组氨酸的连接。这些结果表明结合水、谷氨酸和组氨酸铜配体在质子易位机制中的关键作用。
We address the molecular mechanism by which the haem-copper oxidases translocate protons. Reduction of O2to water takes place at a haem iron-copper (CuB) centre, and protons enter from one side of the membrane through a ‘channel’ structure in the enzyme. Statistical-mechanical calculations predict bound water molecules within this channel, and mutagenesis experiments show that breaking this water structure impedes proton translocation. Hydrogen-bonded water molecules connect the channel further via a conserved glutamic acid residue to a histidine ligand of CuB. The glutamic acid side chain may have to move during proton transfer because proton translocation is abolished if it is forced to interact with a nearby lysine or arginine. Perturbing the CuBligand structure shifts an infrared mode that may be ascribed to the OH stretch of bound water. This is sensitive to mutations of the glutamic acid, supporting its connectivity to the histidine. These results suggest key roles of bound water, the glutamic acid and the histidine copper ligand in the mechanism of proton translocation.