REGULATION AND STRUCTURE OF THE MER OPERON

我们将在分子水平上描述 普遍存在的细菌质粒编码基因座赋予汞 电阻（mer）。 这很常见，但从生物化学上来说， 不寻常的是，解毒系统发挥了重要作用， 汞化合物的微生物循环，包括神经毒素 自然界中的化合物甲基汞。 mer操纵子包括 Hg（II）运输系统，将有毒阴离子输送到 胞质酶Hg（II）还原酶（HR）。 HR，在结构上 与谷胱甘肽还原酶有关， Hg（II）转化为相对无毒的挥发性Hg（O）。 而 人力资源机制是相对较好理解的， Hg（II）的迁移系统尚未阐明。 操纵子 在merR基因的正转录控制下， 它本身是负向自我调节的;然而， 诱导物和操纵子控制的分子细节并不 知道的 首先，将使用遗传和生物化学技术 检测转录起始和终止， 降解，以及操纵子翻译调控的作用 表情 第二，将对运输过程进行研究， 强调他们的内在利益，但也因为 理解操纵子表达的调节依赖于知道 Hg（II）如何在存在和不存在的情况下进入细胞 关于Mer 所有mer基因中的位点或功能特异性突变体将 可以通过多种体外和体内方法来寻求。 最后， 几种遗传学方法将被用来发现什么作用， 宿主细菌细胞在mer功能的表达中起作用。

We will describe at a molecular level the mechanism of the ubiquitous bacterial plasmid-encoded locus conferring mercury resistance (mer). This very commonly found, but biochemically unusual, detoxification system plays a significant role in the microbial cycling of mercury compounds, including the neurotoxic compound methyl mercury, in nature. The mer operon includes a Hg(II) transport system which delivers the toxic anion to the cytosolic enzyme Hg(II) reductase (HR). HR, which is structurally and mechanistically related to glutathione reductase, reduces Hg(II) to volatile Hg(O) which is comparatively non-toxic. While the HR mechanism is relatively well-understood, the mechanism of the Hg(II) transport system has not been elucidated. The operon is under positive transcriptional control of the merR gene which itself is negatively autoregulated; however, the precise nature of the inducer and the molecular details of operon control are not known. Firstly, genetic and biochemical techniques will be used to examine transcription initiation and termination, mRNA degradation, and the role of translational regulation in operon expression. Secondly, studies of the transport process will be emphasized for their intrinsic interest but also because understanding regulation of operon expression depends on knowing how Hg(II) enters the cell both in the presence and in the absence of mer. Site- or function-specific mutants in all mer genes will be sought by a variety of in vitro and in vivo methods. Finally, several genetic approaches will be used to discover what role the host bacterial cell plays in the expression of mer functions.