REGULATION AND STRUCTURE OF THE MER OPERON

决定对汞离子（Hg（II））的抗性的基因被携带 在革兰氏阴性菌和革兰氏阴性菌中， 革兰氏阳性菌。 质粒确定的HgCl 2抗性是由于 通过Hg（II）还原酶将Hg（II）酶促还原为Hg（O）。 这 还原通过将汞离子转化为挥发性的惰性的 form. Hg（II）还原酶是一种细胞内黄素蛋白， 需要NADPH作为辅助因子。 这种酶似乎类似于 二硫键-氧化还原酶如谷胱甘肽还原酶和硫辛酰胺 脱氢酶。 汞（II）还原酶（merA）和汞（II）摄取功能 （merT），是耐汞（mer）操纵子的一部分，其可由 亚毒性水平的氯化汞 正作用调节功能（merR） 似乎是导致这种诱导的原因 我们有特点的 肽编码的mer操纵子，并已构建初步 操纵子的物理和遗传图谱， 传统和分子遗传学。 我们计划将物理和 操纵子的遗传图谱，通过使用体外诱变的操纵子， 操纵子DNA和突变体的生化和遗传特性 衍生物. 我们主要关注的是对 操纵子的调节。 我们将克隆反式作用的基因 在分子水平上研究其相互作用 merP启动子，我们已经从操纵子中克隆了它。 我们 将利用mer-lac操纵子融合来发现无偿诱导剂， 操纵子的抗诱导剂。 我们还将特别诱变 Hg（II）还原酶结构基因和Hg（II）还原酶的结构基因 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.