REGULATION AND STRUCTURE OF THE MER OPERON

决定对汞离子(汞(II))抗性的基因被携带 革兰氏阴性杆菌和肺炎克雷伯菌中多种耐药质粒的研究 革兰氏阳性细菌。质粒决定的HgCl2抗性是由于 汞(II)还原酶将汞(II)还原为汞(O)。这 还原通过将汞离子转化为挥发性的惰性离子来解毒 形式。汞(II)还原酶是一种胞内黄素蛋白， 需要NADPH作为辅因子。这种酶似乎类似于 谷胱甘肽还原酶和硫胺等二硫键氧化还原酶 脱氢酶。汞(II)还原酶(MERA)和汞摄取功能 (MERT)是汞抗性(MER)操纵子的一部分，该操纵子可由 亚毒性水平的氯化汞。积极作用的调节功能(MERR) 似乎是导致这种诱导的原因。我们已经将 由Mer操纵子编码的多肽，已初步构建 使用两种技术的操纵子的物理和遗传图谱 传统遗传学和分子遗传学。我们计划将身体上和身体上 通过对操纵子的体外诱变获得操纵子的遗传图谱 操纵子DNA与突变体的生化和遗传特征 衍生品。我们主要关注对 操纵者的规则。我们将克隆反式作用基因 调控元件MERR及其在分子水平上的相互作用 与我们已经从操纵子克隆的启动子MERP。我们 将利用紫胶操纵子融合来发现免费的诱导子和 操纵子的抗诱导剂。我们还将专门突变 汞(II)还原酶结构基因和汞(II)的结构基因 摄取蛋白质，以剖析其作用机制。

The genes which determine resistance to mercuric ion (Hg(II)) are carried on many antibiotic resistance plasmids in both Gram-negative and Gram-positive bacteria. Plasmid-determined HgCl2-resistance is due to enzymatic reduction of Hg(II) to Hg(O) by the Hg(II) reductase. This reduction detoxifies the mercuric ion by converting it to a volatile, inert form. The Hg(II) reductase is an intracellular, flavoprotein which requires NADPH as a cofactor. This enzyme appears to be similar to the disulfide-oxidoreductases such as glutathione reductase and lipoamide dehydrogenase. The Hg(II) reductase (merA), and an Hg(II) uptake function (merT), are part of a mercury resistance (mer) operon which is inducible by sub-toxic levels of HgCl2. A positively acting regulatory function (merR) appears to be responsible for this induction. We have characterized the peptides encoded by the mer operon and have constructed preliminary physical and genetic maps of the operon using the techniques of both conventional and molecular genetics. We plan to correlate the physical and genetic maps of the operon through the use of in vitro mutagenesis of the operon DNA and biochemical and genetic characterization of the mutant derivatives. We are principally concerned with the analysis of the regulation of the operon. We will clone the gene for the trans-acting regulatory element, merR and study, at the molecular level, its interaction with merP, a promoter which we have already cloned from the operon. We will exploit mer-lac operon fusions to discover gratuitous inducers and anti-inducers of the operon. We will also specifically mutagenize the Hg(II) reductase structural gene and the structural genes for the Hg(II) uptake proteins in order to dissect their mechanism of action.