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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >IDENTIFICATION OF A FUNCTIONAL WATER CHANNEL IN CYTOCHROME P450 ENZYMES
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IDENTIFICATION OF A FUNCTIONAL WATER CHANNEL IN CYTOCHROME P450 ENZYMES

机译：细胞色素P450酶中功能性水通道的鉴定

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Cytochrome P450 enzymes are monooxygenases that contain a functional heme b group linked to a conserved cysteine with a thiolate bond, In the native state, the central iron atom is hexacoordinated with a covalently bound water molecule, The exclusion of solvent molecules from the active site is essential for efficient enzymatic function, Upon substrate binding, water has to be displaced from the active site to prevent electron uncoupling that results in hydrogen peroxide or water, In contrast to typical hemoproteins, the protein surface is not directly accessible from the heme of cytochromes P450, We postulate a two-state model in which a conserved arginine, stabilizing the heme propionate in all known cytochrome P450 crystal structures, changes from the initial, stable side-chain conformation to another rotamer (metastable), In this new state, a functional water channel (aqueduct) is formed from the active site to a water cluster located on the thiolate side of the heme, close to the protein surface, This water cluster communicates with the surface in the closed state and is partly replaced by the flipping arginine side chain in the open state, allowing water molecules to exit to the surface or to reaccess the active site, This two-state model suggests the presence of an exit pathway for water between the active site and the protein surface. [References: 45]
机译：细胞色素P450酶是单加氧酶，其包含通过硫醇键与保守的半胱氨酸相连的功能性血红素b基团，在天然状态下，中心铁原子与共价键合的水分子进行六配位，从活性位点排除溶剂分子是对于有效的酶功能至关重要，在与底物结合后，必须将水从活性位点移开，以防止产生过氧化氢或水的电子解偶联。与典型的血红蛋白相比，不能从细胞色素P450的血红素直接进入蛋白质表面，我们假设一个二态模型，其中一个保守的精氨酸，在所有已知的细胞色素P450晶体结构中稳定丙酸血红素，从最初的稳定侧链构象变为另一个旋转异构体（易位），在这种新状态下，从活性部位到位于血红素硫醇盐侧，靠近血红素的水簇形成水通道（渡槽）。蛋白质表面，该水团簇在闭合状态下与表面连通，并在开放状态下部分被翻转的精氨酸侧链取代，从而使水分子离开表面或重新进入活性位点，这种两态模型表明活性位点和蛋白质表面之间存在水的出口路径。 [参考：45]

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