REGULATION AND STRUCTURE OF THE MER OPERON

我们将研究细菌质粒中的金属反应基因调控- 测定抗汞操纵子。mer位点非常 广泛存在于真细菌中，并介导无机和 有机汞化合物汞结合基序的惊人保守性 人类铜储存疾病中蛋白质改变的蛋白质 （门克斯病和威尔逊病）强调了mer作为一种 了解人类接触有毒金属的模型。此外，急性或 动物宿主长期接触汞化合物会导致 在携带mer基因座的细菌的正常植物群中增殖。 在细菌中，汞解毒基因的表达是 由一种新的汞结合转录调节因子MerR控制。 因此，在该系统中， 过渡金属调控基因的模型，并已被发现， 有几个不寻常的方面没有看到基因调控的非金属 代谢物。(l)我们会用分子遗传学来探测 具有mer操纵子-启动子区域的野生型和突变型merR蛋白 并与RNA聚合酶，以建立分子基础， 转录抑制和激活。(2)我们发现， 表达也受过早转录终止的控制 (i.e. mer具有非常有效的中间操纵子转录衰减子）。我们 将利用遗传学来剖析这种衰减器的元素， 并表征所涉及的顺式和反式作用剂。 (3)我们有 最近发现了宿主细胞氢过氧化物酶 （包括过氧化氢酶）在抗汞性的表达中， 这一作用，并探讨其他宿主染色体基因的重要汞 解毒(4)我们还将开始一个新的项目， 通过分离识别金属的merR突变体， 汞以外的其他物质，并通过使用 NMR、ESR和共振拉曼光谱。

We will study metal-responsive gene regulation in the bacterial plasmid- determined mercury (Hg) resistance (mer) operon. The mer locus is very widely found in eubacteria and mediates detoxification of inorganic and organic Hg compounds. The striking conservation of Hg binding motifs of mer proteins in the proteins altered in the human copper storages diseases (Menkes' and Wilson's diseases) underscores the importance of mer as a model for understanding human exposure to toxic metals. Moreover, acute or chronic exposure of an animal host to mercury compounds results in the proliferation in the normal flora of bacteria which carry the mer locus. In the bacterium, expression of the mercurial detoxification genes is controlled by a novel Hg-binding transcriptional regulator, MerR. Mercury-responsive regulation of gene expression in this system is, thus, a model for regulation of genes by transition metals and has been found to have several unusual aspects not seen in gene regulation by non-metallic metabolites. (l) We will use molecular genetics to probe the interactions of wildtype and mutant merR proteins with the mer operator-promoter region and with RNA polymerase in order to establish the molecular basis for transcriptional repression and activation. (2) We have discovered that mer expression is also controlled by premature transcriptional termination (i.e. mer has a very efficient mid-operon transcriptional attenuator). We will use genetics to dissect the elements of this attenuator and identify and characterize the cis- and trans-acting agents involved. (3) We have recently discovered a surprising role for the host cell hydroperoxidases (including catalase) in the expression of Hg resistance and will define this role and explore other host chromosomal genes important in Hg detoxification. (4) We will also begin a new project on the interaction of MerR with metal ions by isolating merR mutants which recognize metals other than Hg and by characterizing their purified protein products using NMR, ESR, and resonance Raman spectroscopy.