Department of Biochemistry, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA.
Biochemistry. 2009 Dec 29;48(51):12104-12. doi: 10.1021/bi9011435.
Cytochrome P450 reductase (CPR) is a tethered membrane protein which transfers electrons from NADPH to microsomal P450s. We show that the lipid bilayer has a role in defining the redox potential of the CPR flavin domains. In order to quantitate the electrochemical behavior of this central redox protein, full-length CPR was incorporated into soluble nanometer scale discoidal membrane bilayers (nanodiscs), and potentials were measured using spectropotentiometry. The redox potentials of both FMN and FAD were found to shift to more positive values when in a membrane bilayer as compared to a solubilized version of the reductase. The potentials of the semiquinone/hydroquinone couple of both FMN and FAD are altered to a larger extent than the oxidized/semiquinone couple which is understood by a simple electrostatic model. When anionic lipids were used to change the membrane composition of the CPR-nanodisc, the redox potential of both flavins became more negative, favoring electron transfer from CPR to cytochrome P450.
细胞色素 P450 还原酶（CPR）是一种连接在膜上的蛋白质，它将电子从 NADPH 转移到微粒体 P450 上。我们表明，脂质双层在定义 CPR 黄素结构域的氧化还原电位方面起着作用。为了定量研究这种核心氧化还原蛋白的电化学行为，全长 CPR 被整合到可溶性纳米级盘状膜双层（纳米盘）中，并使用光谱电化学法测量电位。与还原酶的可溶形式相比，FMN 和 FAD 的氧化还原电位在膜双层中均向更正的数值移动。FMN 和 FAD 的半醌/氢醌偶对的电位变化大于氧化/半醌偶对，这可以通过简单的静电模型来理解。当使用阴离子脂质来改变 CPR-纳米盘的膜组成时，两种黄素的氧化还原电位变得更负，有利于电子从 CPR 向细胞色素 P450 转移。
