CAUSE & EFFECT OF DIMER ASYMMETRY IN MERCURIC REDUCTASE

汞离子还原酶催化的双电子还原 Hg（II）转化为元素汞是细菌转化的关键步骤 汞（II）和有机汞的解毒。 述酶是 每个二聚体具有两个界面活性位点同源二聚体蛋白， 大量的证据表明sense的氧化还原和/或配体状态 对方. 我们最近发现，在氧化 半反应的酶与庞大的巯基配体汞（II） 化合物，与体内底物相当，亚基间 相互作用似乎是关键的催化循环， 简单的Hg（II）化合物可以绕过正常的进入途径， 相应的亚基间相互作用。 我们使用MidasPlus来识别 小汞和大汞（II）基质的拟议进入途径 目前正在使用该软件来帮助识别 沿着这些途径的另外的残基可能参与 配体交换过程，并代表突变的目标 分析. 我们还使用该软件来帮助可视化 蛋白质的静电势，特别是作为配体或 氧化还原状态的变化与假设，这可能是一个关键因素， 在子单位间的通信。 一个新的方向，我们计划 追求是酶的金属离子特异性的再工程。 随着我们最近对结合途径的鉴定，我们将使用 图形来考虑我们可能是什么类型的金属离子络合物， 能够适应和做什么改变来完成任务。

Mercuric ion reductase catalyzes the two-electron reduction of Hg(II) to elemental mercury as the key step in bacterial detoxification of Hg(II) and organomercuricals. The enzyme is a homodimeric protein with two interfacial active sites per dimer, which extensive evidence indicates sense the redox and/or ligand state of each other. We have recently found that in the oxidative half-reaction of the enzyme with bulky thiol-liganded Hg(II) compounds, comparable to the in vivo substrate, intersubunit interactions appear to be critical in the catalytic cycle while simpler Hg(II) compounds can bypass the normal entry route and the corresponding intersubunit interactions. We use MidasPlus to identify proposed entry pathways for the small verses large Hg(II) substrates and are currently using the software to aid in the identification of additional residues along these pathways that may participate in the ligand exchange processes and represent targets for mutational analysis. We are also using the software to help visualize the electrostatic potential of the protein, especially as the liganded or redox state changes with the hypothesis that this may be a key element in the intersubunit communication. A new direction that we plan to pursue is a reengineering of the metal ion specificity of the enzyme. With our recent identification of pathways for binding, we will use the graphics to consider what types of metal ion complexes we might be able to accomodate and what changes to make to accomplish the task.