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）是关键的末端呼吸酶，负责利用需氧生物体能量产生所需的分子氧的氧化能力。从化学角度来看，反应的净产物是两当量的水，是通过分子氧的彻底还原以及泵送 H 穿过线粒体膜产生化学渗透势而产生的。由于 CcO 的重要生化功能，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，以肌张力低下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，老年人群衰老过程引起的 CcO 突变会导致肌肉质量减少以及其他退化过程，这使得 CcO 的研究成为一个有吸引力的目标。 CcO 中分子氧还原的活性位点在金属蛋白中是独一无二的，它吸引了合成学家和生物化学家的关注，其共同目标是了解最终导致内在反应性的结构-功能关系。尽管进行了数十年的深入研究，但对动力学捕获的酶中间体的直接光谱探测尚未提供表征 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以及大量酶数据。模型复合物将用于测试过氧中间体在 CcO 催化过程中的可行性，如理论预测的那样。结合CcO态PM的直接光谱探测，这项研究将进一步测试活性位点的可能性 酪氨酸作为氢原子供体。最后，自旋态、自旋耦合和铜离子密度的影响将为氧裂解坐标的方向提供重要的见解，并为活性位点结构元素提供基于函数的基本原理。这些研究需要应用先进的光谱学，如共振拉曼、X 射线和光磁圆二色性、电子顺磁共振和 X 射线吸收，与 DFT 等电子结构方法相结合，将结果与酶催化联系起来。因此，该研究需要为受训者提供丰富的培训内容。 公共健康相关性：这些研究将产生有关 CcO 还原双氧的分子水平详细信息，有助于了解 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.