Tyrosine Assisted Electron Transfer in Modified Azurins

描述（由申请人提供）：生物催化和能量转导通常依赖于蛋白质内部和蛋白质之间的长距离（>20 E）快速电荷传输。许多氧化还原酶，特别是那些参与强化学键（例如O-H，O=O，C-H）活化的氧化还原酶，也需要在高电位下进行电荷传输。长距离和高电位电荷传输的组合对进行这些反应的酶支架提出了严格的设计要求。许多氧化还原酶使用具有氧化还原活性的氨基酸色氨酸（W）和酪氨酸（Y）作为氧化还原“中途站”，以将长距离电荷传输打断为较短的电子隧穿步骤。这就是所谓的“跳跃”。“这项研究将研究影响人工蓝铜天青模型系统中Y跳跃的因素。所有这些系统都由位于天青-CuI中心和（蛋白质）表面附着光敏剂之间的酪氨酸残基组成。我们的天青蛋白模型是专门设计来解释质子转移，必须伴随酪氨酸的氧化还原反应。引入酸性酪氨酸，3-硝基酪氨酸（目标1），将允许通过酪氨酸跳跃的研究，其中质子转移是不重要的。生物Y-跳跃系统中的一个重要结构基序是在Y的酚质子附近定位碱性部分，其在Y氧化时接受质子。一系列的突变天青蛋白将产生和研究质子接受基团，如天冬氨酸或组氨酸，位于附近的Y（目标2）。预期这些碱基的位置将促进通过酪氨酸的可逆电子转移。通过使用从目标1和2收集的设计标准，将探索通过Y发生超远程电荷传输（> 30 E）的天青蛋白模型（目标3）。 公共卫生相关性：涉及氨基酸酪氨酸的还原和氧化（氧化还原）途径在广泛的代谢过程中至关重要。许多疾病与氧化还原途径的失败、中断或故障有关。阐明控制酪氨酸生物氧化还原化学的基本因素将导致对疾病机制的更深入理解，并为新疗法的开发提供信息。

DESCRIPTION (provided by applicant): Biological catalysis and energy transduction often rely on rapid charge transport over great distances (>20 E) within and between proteins. Many redox enzymes, especially those involved in the activation of strong chemical bonds (e.g. O-H, O=O, C-H), also require charge transport at high potentials. The combination of long-range and high potential charge transport places strict design requirements on enzyme scaffolds that carry out these reactions. Numerous redox enzymes use the redox active amino acids tryptophan (W) and tyrosine (Y) as redox 'way stations' to break long-range charge transport into shorter electron tunneling steps. This is known as 'hopping.' This research will examine the factors that influence hopping through Y in artificial blue-copper azurin model systems. All of these systems consist of a tyrosine residue situated between the azurin-CuI center and a (protein) surface attached photosensitizer. Our azurin models are specifically designed to account for the proton transfer that must accompany redox reactions of tyrosine. Introduction of an acidic tyrosine, 3-nitro-tyrosine (Aim 1), will allow for studies of hopping via tyrosinate, where proton transfer is not important. An important structural motif in biological Y-hopping systems is the positioning of a basic moiety near the phenolic proton of Y, which accepts the proton upon Y oxidation. A series of mutant azurins will be produced and studied where proton accepting groups, such as aspartate or histidine, are situated near Y (Aim 2). It is expected that the position of these bases will facilitate reversible electron transfer via tyrosine. By using the design criteria gleaned from Aims 1 and 2, azurin models where ultra-long-range charge transport (> 30 E) occurs through Y will be explored (Aim 3). PUBLIC HEALTH RELEVANCE: Reduction and oxidation (redox) pathways that involve the amino acid tyrosine are vital in a wide array of metabolic processes. Numerous diseases are associated with failure, disruption or malfunction of redox pathways. Elucidation of the fundamental factors that control biological redox chemistry of tyrosine will lead to deeper understanding of disease mechanisms and inform the development of new therapies.