Selective Gene Regulation by Manganese and Iron in Bacillus subtilis

该项目旨在确定铁和锰两种重要的环境元素在遗传特征良好的土壤微生物枯草芽孢杆菌基因调控中的作用。在初步研究中，发现了铁或锰或两者都能抑制的基因融合。其中三个金属调控基因被克隆并使用分子遗传学进行了分析。在枯草芽孢杆菌中，铁调节似乎涉及一种与肠内Fur蛋白在DNA结合特异性上相似的调节蛋白。到目前为止，还没有从任何革兰氏阳性生物体中发现毛皮同源物。与肠道皮毛蛋白不同，枯草芽孢杆菌的铁调节蛋白似乎对锰有歧视。在肠道生物中，锰可以模拟铁，抑制铁载体的生物合成和其他铁调节功能。相比之下，枯草芽孢杆菌中嗜铁细胞的产生对锰的抑制不敏感。相反，我们对高度敏感的锰特异性转录控制的检测表明存在一种新型的金属调节系统。这一系统可能部分解释了锰离子对芽孢杆菌和其他革兰氏阳性菌次生代谢产物产生的许多显著影响。在芽胞杆菌中，铁和锰似乎控制着不同但重叠的规则。例如，我们已经确定了一组启动子融合物，它们选择性地对铁而不是锰作出反应，或者对锰而不是铁作出反应。在一种情况下，我们从基因上分离了铁和锰的反应。这些结果表明，这些元件发挥特异性和独立的转录控制。然而，允许细胞选择性地检测这些元素并介导适当的转录反应的机制在很大程度上是未知的。我们将定义铁和锰对基因调控的整体影响，并确定选择性基因调控的分子基础。利用蛋白质凝胶电泳，我们将确定金属调控蛋白组，并确定不同金属离子调控之间的串扰程度。将利用转座子Tn917-lacZ分离金属调控基因，并确定金属调控的DNA序列决定因素。这将为相关金属调控蛋白的遗传和生化鉴定提供必要的工具。这些调节蛋白的特性有望揭示蛋白质如何区分化学上相似的金属离子，从而影响选择性转录控制。这项资助提供了关于细菌如何对环境作出反应的信息，特别是关于金属的存在。＊＊＊

9317425 Helmann This project seeks to define the role of two environmentally important elements, iron and manganese, in gene regulation in the genetically well-characterized soil microbe Bacillus subtilis. In preliminary studies, gene fusions repressible by iron or manganese or both were identified. Three of these metal-regulated genes were cloned and analyzed using molecular genetics. In B. subtilis, iron regulation appears to involve a regulatory protein similar in DNA binding specificity to the enteric Fur protein. There have been no Fur homologs described to date from any gram positive organisms. Unlike the enteric Fur protein, the B. subtilis iron-regulatory protein appears to discriminate against manganese. In the enteric organisms manganese can mimic iron and repress siderophore biosynthesis and other iron-regulated functions. In contrast, production of sideropheres in B. subtilis is insensitive to manganese repression. Conversely, our detection oh highly sensitive manganese-specific transcriptional control suggests the presence of a novel type of metalloregulatory system. This system may account, in part, for the many striking effects of manganous ion on production of secondary metabolities in Bacilli and other gram positive organisms. In Bacilli, iron and manganese appear to control distinct, but overlapping regulons. For example, we have identified sets of promoter fusions that respond selectively to iron but not manganese or to manganese but not iron. In one case, we have genetically separated the iron and manganese responses. These results suggest that these elements exert specific and independent transcriptional control. However, the mechanisms allowing cells to selectively detect these elements and mediated appropriated transcriptional responses are largely unknown. We will define the global effects of iron and manganese on gene regulation and determine the molecular basis of selective gene regulation. Using protein gel electrophores is, we will identify sets of metalloregulated proteins and determine the extent of cross-talk among the different metal ion regulons. Metalloregulated genes will be isolated using transposon Tn917-lacZ and the DNA sequence determinants of metalloregulation defined. This will provide the tools necessary for the genetic and biochemical identification of the relevant metalloregulatory proteins. Characterization of these regulatory proteins promises to shed light on how proteins can discriminate chemically similar metal ions to effect selective transcriptional control. %%% This grant provides information on how bacteria respond to their environment, especially as regards the presence of metals. ***