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）是一种关键的终端呼吸酶，负责利用有氧生物中产生能量所必需的双氧的氧化能力。化学上，反应的净产物是两个等价物的水，是通过彻底还原双氧同时泵送H+穿过线粒体膜产生化学渗透势而产生的。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，以低张力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，在老年人群中，由衰老过程引起的CcO突变导致肌肉质量减少以及其他退行性过程，这使得CcO的研究成为一个有吸引力的目标。CcO中的二氧还原活性位点在金属蛋白中是独一无二的，这引起了合成化学家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。尽管经过数十年的深入研究，对动力学捕获的酶中间体的直接光谱探测还没有提供表征O-O键断裂机制所需的详细信息。因此，这些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。模型配合物将用于测试过氧中间体在CcO催化过程中的可行性，正如理论预测的那样。结合CcO状态PM的直接光谱探测，本研究将进一步测试活性位点的可能性

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.