Spectroscopic and Computational Investigation of Cytrochrome C Oxidase and Models

描述(由申请人提供)：细胞色素c氧化酶(CcO)是关键的，终端呼吸酶，负责利用氧气的氧化能力，在有氧生物体中产生能量所必需的。从化学上讲，该反应的净产物是两个等量的水，通过穷尽地还原氧气并通过线粒体膜泵入氢来产生化学渗透势而产生。由于CcO的基本生化功能，与功能失调突变相关的病理通常被证明与生命不相容。例如，以低眼压和心脑肌病为特征的严重婴儿疾病与CcO功能减弱有关。同样，老年人群衰老过程中引起的CcO突变在其他退化过程中有助于减少肌肉质量，使对CcO的研究成为一个吸引人的目标。CcO中氧还原的活性部位在金属蛋白中是独一无二的，这引起了合成和生物化学家的关注，他们的共同目标是了解最终导致内在反应性的结构-功能关系。尽管经过了几十年的紧张研究，但对动力学捕获的酶中间体的直接光谱探测并没有提供表征O-O键断裂机制所需的详细信息。因此，信息必须来自小分子模型研究和理论，并结合大量的酶数据。模型络合物将被用来检验理论预测的在CCOO催化过程中使用过氧基中间体的可行性。结合对CCO态PM的直接光谱探测，这项研究将进一步测试活性中心的可能性 酪氨酸起氢原子供体的作用。最后，自旋态、自旋耦合和铜离子密度的影响将对氧裂解配位的方向提供重要的认识，并为活性中心结构元素提供一个基于函数的理论基础。这些研究需要应用先进的光谱学，如共振拉曼光谱、X射线和光磁圆二色谱、电子顺磁共振和X射线吸收，并与电子结构方法(如密度泛函理论)相结合，将结果与酶催化相关联。因此，这项研究需要为受训者提供丰富的培训内容。 与公共健康相关：这些研究将提供有关CcO还原二氧化碳的分子水平的细节，这有助于理解CcO突变的发病机制，并可能作为“绿色”化学催化剂的基础。

DESCRIPTION (provided by applicant): Cytochrome c oxidase (CcO) is the key, terminal respiratory enzyme responsible for harnessing the oxidative power of dioxygen necessary for energy production in aerobic organisms. Chemically, the net product of the reaction is two equivalents of water, generated by exhaustive reduction of dioxygen concomitantly with pumping of H+ across the mitochondrial membrane to generate a chemiosmotic potential. Due to CcO's essential biochemical function, the pathology associated with dysfunctional mutation generally proves incompatible with life. For example, severe infantile diseases characterized by hypotonia and cardioencephalomyopathy have been linked to attenuated CcO function. Similarly, mutations in CcO caused by the aging process in older populations contribute to reduced muscle mass among other degenerative processes, making study of CcO an engaging target. The active site of dioxygen reduction in CcO is unique among metalloproteins, which attracts the attention of synthetic and biochemists alike with the common goal of understanding the structure-function relationships that ultimately lead to the intrinsic reactivity. Despite decades of intense research effort, direct spectroscopic probing of kinetically trapped enzymatic intermediates has not provided information in a level of detail necessary for characterization of the mechanism of O-O bond rupture. Therefore, the information must come from small molecule model studies and theory in conjunction with the large body of enzymatic data. Model complexes will be used to test the feasibility of a peroxo intermediate during CcO catalysis as predicted by theory. Combined with direct spectroscopic probing of CcO state PM, this study will further test the possibility of an active site tyrosine functioning as a hydrogen atom donor. Finally, the effect of spin state, spin coupling, and copper ion denticity will shed important insight into the direction of the oxygen cleavage coordinate and provide a function based rationale for active site structural elements. The studies require application of advanced spectroscopies such as resonance Raman, X-ray and optical magnetic circular dichroism, electron paramagnetic resonance, and X-ray absorption to be combined with electronic structure methods such as DFT to relate the results to enzymatic catalysis. Thus, the study entails a rich training component for the Trainee. PUBLIC HEALTH RELEVANCE: These studies will yield molecular level details concerning dioxygen reduction by CcO, insight useful for understanding pathogenesis of CcO mutation and perhaps as a basis for "green" chemical catalysts.