Crystallographic and Mechanistic Studies of Cytochrome c Peroxidase

研究细胞色素c过氧化物酶（CcP）与细胞色素c之间的电子转移反应。CcP是一种34000毫瓦特的单体血红素酶，使用细胞色素c作为电子供体，催化过氧化氢还原为水。CcP催化循环的一个步骤涉及CcP血红素和细胞色素c之间的快速电子转移，尽管血红素边缘至少相隔17。本实验室测定了CcP的晶体结构及其与细胞色素c形成的络合物。这些晶体结构将用于指导定点诱变实验，旨在干扰两个血红素之间电子转移途径的特定元素。特定突变对结构和电子转移速率的影响将使用晶体学和瞬态光谱技术进行评估。该结果将有助于确定CcP血红素和细胞色素c之间长距离电子转移反应所需的结构元素。%%%所有需氧生物从氧到水的转化中获得生物合成反应所需的能量。这是由一个高度有序的酶系统完成的，该系统将电子从代谢物转移到氧气中，同时保留该反应产生的一些能量用于合成反应。细胞电子传递系统由嵌入在蛋白质中的各种金属中心组成。很明显，电子在金属中心之间转移，而电子转移是由金属中心周围的蛋白质控制的，但对于蛋白质基质如何使这些电子转移反应高效和高度特异性知之甚少。作为理解这一过程的第一步，本研究将研究如何在两个定义良好的蛋白质分子的金属中心之间快速进行电子转移。这项工作的更大目标是了解有氧生物如何实现生存所需的高效和特定的电子转移反应。＊＊＊

9420845 Kraut The electron transfer reaction between cytochrome c peroxidase (CcP) and cytochrome c will be examined. CcP is a 34,000 M.W. monomeric heme enzyme that catalyses the reduction of peroxide to water, using cytochrome c as the electron donor. One step in the catalytic cycle of CcP involves rapid electron transfer between the hemes of CcP and cytochrome c, although the heme edges are separated by at least 17 . The crystal structure of CcP and the complex formed between CcP and cytochrome c have been determined in this laboratory. These crystal structures will be used to guide site-directed mutagenesis experiments aimed at perturbing specific elements of the electron transfer pathway between the two hemes. The effect of specific mutations on structure and electron transfer rates will be evaluated using crystallography and transient spectroscopy techniques. The results will help to define the structural elements that are required for the long distance electron transfer reaction between the hemes of CcP and cytochrome c. %%% All aerobic organisms obtain the energy required for biosynthetic reactions from the conversion of oxygen to water. This is accomplished by a highly ordered enzyme system that transfers electrons from metabolites to oxygen, while preserving some of the energy from this reaction for use in synthetic reactions. The cellular electron transfer system consists of a variety of metal centers that are embedded in proteins. It is clear that the electrons are transferred between the metal centers, and the electron transfer is controlled by the protein surrounding the metal centers, but little is known about how the protein matrix makes these electron transfer reactions efficient and highly specific. As a first step in understanding this process, this investigation will examine how electron transfer is conducted rapidly between the metal centers of twm well-defined protein molecules. The larger goal of the work is to understand how aerobic organisms achieve the efficient and specific electron transfer reactions that are required for survival. ***