Henry Wellcome Laboratories for Structural Biology, Department of Biochemistry, University of Leicester, Henry Wellcome Building, Leicester LE1 9HN, UK.
Structure. 2013 Sep 3;21(9):1581-9. doi: 10.1016/j.str.2013.06.022. Epub 2013 Aug 1.
NADPH-cytochrome P450 reductase is a key component of the P450 mono-oxygenase drug-metabolizing system. There is evidence for a conformational equilibrium involving large-scale domain motions in this enzyme. We now show, using small-angle X-ray scattering (SAXS) and small-angle neutron scattering, that delivery of two electrons to cytochrome P450 reductase leads to a shift in this equilibrium from a compact form, similar to the crystal structure, toward an extended form, while coenzyme binding favors the compact form. We present a model for the extended form of the enzyme based on nuclear magnetic resonance and SAXS data. Using the effects of changes in solution conditions and of site-directed mutagenesis, we demonstrate that the conversion to the extended form leads to an enhanced ability to transfer electrons to cytochrome c. This structural evidence shows that domain motion is linked closely to the individual steps of the catalytic cycle of cytochrome P450 reductase, and we propose a mechanism for this.
NADPH-细胞色素 P450 还原酶是 P450 单加氧酶药物代谢系统的关键组成部分。有证据表明，该酶中存在涉及大规模结构域运动的构象平衡。我们现在使用小角度 X 射线散射 (SAXS) 和小角度中子散射表明，向细胞色素 P450 还原酶传递两个电子会导致这种平衡从类似于晶体结构的紧凑形式向扩展形式转移，而辅酶结合有利于紧凑形式。我们提出了一种基于核磁共振和 SAXS 数据的酶扩展形式模型。通过改变溶液条件和定点突变的影响，我们证明向扩展形式的转变导致向细胞色素 c 转移电子的能力增强。这种结构证据表明，结构域运动与细胞色素 P450 还原酶的催化循环的各个步骤密切相关，我们为此提出了一种机制。
