Regulation and Structure of the mer Operon

金属离子在许多酶的活性中扮演着重要的角色，生物系统也对金属元素进行非常细微的区分，以控制基本的信息转导过程。此外，含有活性部位的巯基的蛋白质(潜在的金属结合靶标)在DNA复制和修复中起着关键作用。目前，我们对是什么决定了特定的蛋白质-金属相互作用以及替代金属如何调节蛋白质行为的理解还不完全。萨默斯研究了细菌的汞抗性(MER)基因座，这是一种由一个小的、汞响应的、DNA结合的转录激活/抑制因子MERR控制的操纵子。她的工作集中在MerR与其同源DNA位点merOP以及与RNA聚合酶的相互作用上。她将使用分子遗传学和生物化学来识别MerR结构域，这些结构域使其能够在诱导前隔离merOP上的RNA聚合酶，以及那些对激活过程中发生的DNA扭曲负责的结构域。她将剖析Mer操纵子和染色体编码的氧化休克调节子之间的关系。最后，她将使用随机和定点突变来获得对汞(II)以外的过渡金属反应的MerR突变体。这些变异的MERR蛋白将在体外检测它们的金属和DNA结合特性。某些微生物能够在对大多数其他生物有毒的化学物质的存在下生长。实现这一点的一种方法是将该化学物质的有毒形式转化为无毒或毒性较低的形式。这项建议调查了调节和控制细菌中一组基因表达的遗传机制，这些基因在汞的解毒中发挥作用。$//

Metal ions figure significantly in the activity of many enzymes biological systems also make very subtle distinctions among metallic elements to control fundamental information transduction processes. Moreover, proteins with active-site sulfhydryl groups (potential metal binding targets) play key roles in DNA replication and repair. Presently, our understanding of what determines specific protein-metal interactions and of how alternative metals can modulate protein behavior is incomplete. Summers studies the bacterial mercury (Hg) resistance (mer) locus, an operon controlled by a small, Hg-responsive, DNA binding, transcriptional activator/repressor, MerR. Her work has focussed on MerR interactions with its cognate DNA site, merOP, and with RNA polymerase. She will use molecular genetics and biochemistry to discern the MerR domains which enable it to sequester RNA polymerase at merOP prior to induction and those responsible for the DNA distortion which takes place during activation. She will dissect the relationship between the mer operon and the chromosomally encoded oxidative shock regulon. Finally, she will employ random and site specific mutagenesis to obtain MerR mutants responsive to transition metals other than Hg(II). These variant MerR proteins will be examined in vitro for their metal and DNA binding properties. %%% Certain micro-organisms have the ability to grow in the presence of chemicals which are toxic to most other organisms. One way this is accomplished is through conversion of the toxic form of the chemical to a non or less toxic form. This proposal investigates the genetic mechanisms which regulate and control the expression of a set of genes in bacteria which function in the detoxification of mercury. $$$//