Electron Transfer in Structurally Engineered Metalloproteins

该项目由无机、生物无机和有机金属项目支持，旨在继续研究影响生物系统中远程电子转移的因素。酵母iso1 -细胞色素c的基因工程突变体将用于这些研究，该突变体在蛋白质周围的不同位点上具有组氨酸残基取代天然氨基酸。通过这些组氨酸位点的络合，引入氧化还原活性发光钌配合物，可以在已知的固定距离上对金属酶的电子转移进行光谱监测。最近发展的激光闪灭技术将用于确定电子转移速率。与以前的方法相比，这种技术有两个主要优点。首先，它允许用天然铁来研究蛋白质，而不是用金属取代的形式；其次，它允许研究更大范围的转移速率。在研究的第二阶段，类似的改良人类肌红蛋白将被用于研究单电子转移到多电子事件的耦合，如铁基（Fe=O）物种的产生。这些研究的总体目标是确定电子在10埃或更大的距离上从供体向受体移动的机制。电子传递是生物系统中最重要的过程之一。这些电子转移的一个有趣的方面是，电子供体和受体经常相隔很远。然而，电子在短距离上的转移理论，在供体和受体轨道重叠的地方，已经发展得很好，电子在远距离上移动的机制还不太清楚。诸如此类的研究可能最终导致更好地治疗某些生理障碍和太阳能转换的新方法。

This project, supported by the Inorganic, Bioinorganic and Organometallic Program, is for continuation of studies of the factors that affect long-range electron transfer in biological systems. Genetically engineered mutants of yeast iso-1-cytochrome c, which have histidine residues substituted for the native amino acid at various sites on the periphery of the protein, will be used for these studies. Introduction of redox active, luminescent ruthenium complexes, by complexation at these histidine sites, allows for the spectroscopic monitoring of electron-transfer to, or from, the metalloenzyme over well-known, fixed distances. A recently developed laser flash-quench technique will be used to determine the electron-transfer rates. This technique has two major advantages for these studies over previous methods. First, it allows for study of the protein with the native iron, rather than a metal substituted version, and second, it permits the study of a much wider range of transfer rates. In a second phase of the research, similarly modified human myoglobins will be used for the study of the coupling of single electron transfers to multielectron events such as generation of a ferryl (Fe=O) species. The overall objective of these studies is to determine the mechanism by which the electron moves from the donor to the acceptor over distances of 10 angstroms and greater. %%% Electron transfer is one of the most important processes in biological systems. An intriguing aspects of these electron transfers is that the electron donor and acceptor are frequently separated by large distances. Whereas theories of electron transfer over short distances, where overlap of donor and acceptor orbitals can occur, is well developed, the mechanism by which the electron moves over long distances is not well understood. Studies such as these may ultimately result in better treatment of certain physiological disorders and in new methods of solar energy conversion.