ELECTRON TRANSFER PROCESSES IN IRON AND COPPER PROTEINS

描述：电子转移(ET)反应，最简单的化学 过程，渗透到生物学中。光合作用、呼吸作用、固氮作用、 药物新陈代谢、DNA合成和免疫反应只是一小部分 在几十个生物过程中，ET反应起着关键作用 角色。任何理解结构和结构之间的关系的努力 氧化还原酶的功能取决于对长程ET的理解。 蛋白质。 先前的理论和实验工作表明，不同的蛋白质 二级结构类型对长程ET的中介作用有显著差异 效率。我们将对距离和距离进行系统测量 (天青素、氨花青素、氨基青兰、 可溶性铜(A)和α-螺旋(细胞色素b(562)蛋白)，以便 确定远程ET效率和氢键在以下方面的作用 这两个结构。 理论模型表明，远程电子对撞机的效率取决于 氧化还原位电子态的相对能量 蛋白质基质(多肽)。从来没有一个明确的实验 证明了这种所谓的隧道能量依赖，然而 可预见的影响可能相当显著。隧道能量在隧道中的作用 远程ET将在距离相关性研究中进行评估 ET在几种蛋白质中的比率是受体还原电位的函数。 在电子转移中，金属络合物经常充当氧化还原位。 蛋白质。长程ET依赖于这些氧化还原的偶联效率 与介入性多肽的结合。由于不同的金属配体 相互作用，这种耦合可以是高度各向异性的。这些因素的影响 不同的配体偶联将在ET的几个研究中被检查 铜蛋白天青素的活性位点突变体。 许多生物氧化还原反应伴随着显著的变化 蛋白质构象。金属蛋白中的一个常见例子是增益或 当金属氧化状态改变时，活性部位的配体的损失。 氧化还原偶联配位变化的动力学后果是 在铜蛋白氨基花青素的ET研究中进行了检测。

DESCRIPTION: Electron-transfer (ET) reactions, the simplest chemical processes, pervade biology. Photosynthesis, respiration, nitrogen fixation, drug metabolism, DNA synthesis, and immune response represent a small subset of the scores of biological processes in which ET reactions play pivotal roles. Any effort to understand the relationship between structure and function in redox enzymes rests on an understanding of long-range ET in proteins. Prior theoretical and experimental work indicates that different protein secondary-structure types mediate long-range ET with markedly different efficiencies. We will perform systematic measurements of the distance and deuterium isotope dependencies of ET rates on beta-sheet (azurin, amicyanin, soluble Cu(a) and alpha-helical (cytochrome b(562) proteins in order to define the long range ET efficiencies and the role of hydrogen bonds in these two structures. Theoretical models indicate that the efficiency of long-range ET depends on the relative energies of the electronic states of the redox sites and the protein matrix (polypeptide). There has never been a clear experimental demonstration of this so-called tunneling-energy dependence, yet the predicted effects can be quite significant. The role of tunneling energy in long-range ET will be evaluated in studies of the distance dependencies of ET rates in several proteins as functions of acceptor reduction potential. Metal complexes frequently serve as redox sites in electron-transfer proteins. Long-range ET depends on the efficiency of coupling these redox sites to the intervening polypeptide. Owing to varied metal-ligand interactions, this coupling can be highly anisotropic. The effects of these disparate ligand couplings will be examined in ET studies of several active-site mutants of the copper protein azurin. Many biological redox reactions are accompanied by significant changes in protein conformation. A common example in metalloproteins is the gain or loss of a ligand at the active site upon change in metal oxidation state. The kinetic consequences of a redox-coupled coordination change will be examined in ET studies of the copper protein amicyanin.