Nature of the Energy Landscape for Gated Electron Transfer in a Dynamic Redox Protein

作者：Sam Hay, Sibylle A. Brenner, Basile Khara, Anne Marie Quinn, Stephen E. J. Rigby, Nigel Shaun Scrutton · 发表于：Journal of the American Chemical Society · 年份：2010 · DOI：10.1021/ja1016206 · 被引用次数：64 · 研究领域：Photochemistry and Electron Transfer Studies、CO2 Reduction Techniques and Catalysts、Electrochemical Analysis and Applications

Conformational control limits most electron transfer (ET) reactions in biology, but we lack general insight into the extent of conformational space explored, and specifically the properties of the associated energy landscape. Here we unite electron-electron double resonance (ELDOR) studies of the diradical (disemiquinoid) form of human cytochrome P450 reductase (CPR), a nicotinamide adenine phosphate dinucleotide (NADPH)-linked diflavin oxidoreductase required for P450 enzyme reduction, with functional studies of internal ET to gain new insight into the extent and properties of the energy landscape for conformationally controlled ET. We have identified multiple conformations of disemiquinoid CPR, which point to a rugged energy landscape for conformational sampling consistent with functional analysis of ET using high-pressure stopped-flow, solvent, and temperature perturbation studies. Crystal structures of CPR have identified discrete "closed" and "open" states, but we emphasize the importance of a continuum of conformational states across the energy landscape. Within the landscape more closed states that favor internal ET are formed by nucleotide binding. Open states that enable P450 enzymes to gain access to electrons located in the FMN-domain are favored in the absence of bound coenzyme. The extent and nature of energy landscapes are therefore accessible through the integration of ELDOR spectroscopy with functional studies. We suggest this is a general approach that can be...