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长距离（bbb20e）的快速电荷传输。许多氧化还原酶，特别是那些参与强化学键（如O- h， O=O, C-H）激活的酶，也需要在高电位下进行电荷传递。远程和高电位电荷传输的结合对进行这些反应的酶支架的设计提出了严格的要求。许多氧化还原酶使用氧化还原活性氨基酸色氨酸(W)和酪氨酸(Y)作为氧化还原“中转站”，将远程电荷传输分解为更短的电子隧穿步骤。这就是所谓的“跳跃”。本研究将探讨在人工蓝铜蓝蛋白模型系统中影响Y跳变的因素。所有这些系统都由位于azurin-CuI中心和（蛋白质）表面附着的光敏剂之间的酪氨酸残基组成。我们的azurin模型是专门设计用于解释必须伴随酪氨酸氧化还原反应的质子转移。引入酸性酪氨酸，3-硝基酪氨酸（Aim 1），将允许通过酪氨酸跳跃的研究，其中质子转移不重要。在生物跳Y系统中，一个重要的结构基序是在Y的酚质子附近定位一个基本片段，它在Y氧化时接受质子。在质子接受基团如天冬氨酸或组氨酸位于Y附近的地方，将产生和研究一系列突变的azurins （Aim 2）。预计这些碱基的位置将促进通过酪氨酸的可逆电子转移。通过使用目标1和目标2中收集的设计标准，将探索通过Y发生超远程电荷输运（bbb30 E）的azurin模型（目标3）。

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.