CONSERVATION BETWEEN RHIZOBIUM NIF, NTR AND DCT GENES

最近的研究与一个双组分模型相一致， 感觉传导和转录调节，适用于 在许多真细菌物种中的许多生物反应。 功能域似乎已经进化到可以重复使用 现有的蛋白质-蛋白质和蛋白质-DNA相互作用， 创造新的监管体系。 验证这些存在 功能域可以通过以下调节来实现 表型后重排现有的结构域在杂交基因的 通过将大量点突变的第二位点回复映射到 展示互动领域。 实验旨在 利用C4-二羧酸转运（dct）、固氮（nif） 和氮同化（ntr）基因，以测试 模型的有效性;结果将同时揭示 生物氮素必需基因表达机制 固定 以前的工作提供了nif结构基因和 合适的启动子：：报告基因构建，调节 基因nifA、ntrB和ntrC，以及交替西格玛因子编码的 在ntrA。 未发表的工作提供了dctA结构基因， 调节基因dctB和dctD。 杂交基因、表达载体 用于产生调节蛋白的dctA：：lacZ融合基因， 报告转录和各种突变株将是 构建了 这些工具将促进表型筛选 为了发现相似的多肽区域是如何在特定的 在苜蓿根瘤菌中调节多种途径的方式。 预计这项研究将引起广泛的学术和实际兴趣 因为相关的基因产物控制植物肿瘤的形成， 农杆菌、芽孢杆菌产孢和磷酸盐清除 和肠道中的趋化性;类似的基因也涉及 几种革兰氏阴性菌感染的起始和维持 通过控制菌毛蛋白基因的表达， 通过柄杆菌属的分化，以及控制 木糖降解基因和羧肽酶G2， 假单胞菌

Recent studies are consistent with a two-component model of sensory transduction and transcriptional regulation that applies to a number of biological responses in many eubacterial species. Functional domains appear to have evolved to make repeated use of existing protein-protein and protein-DNA interactions to create novel regulatory systems. Validating the presence of these functional domains can be achieved by either following regulatory phenotypes after rearranging existing domains in hybrid genes of by mapping second site reversions of numerous point mutations to demonstrate interactive domains. Experiments are designed to utilize C4-dicarboxylate transport (dct), nitrogen fixation (nif) and nitrogen assimilation (ntr) genes of Rhizobium to test the validity of the model; results will simultaneously reveal mechanisms of gene expression essential to biological nitrogen fixation. Previous work provides nif structural genes and appropriate promoter::reporter gene constructions, regulatory genes nifA, ntrB and ntrC, and the alternate sigma factor encoded by ntrA. Unpublished work provides the dctA structural gene and regulatory genes dctB and dctD. Hybrid genes, expression vectors for producing regulatory proteins, a dctA::lacZ fusion gene for reporting transcription and various mutant strains will be constructed. These tools will then facilitate phenotype screening to discover how similar polypeptide regions are used in a specific fashion to regulate numerous pathways in Rhizobium meliloti. Broad academic and practical interest in this study is anticipated because related gene products control plant tumor formation by Agrobacteria, sporulation by Bacillus and phosphate scavenging and chemotaxis in enterics; similar genes are also implicated in initiation and maintenance of infection by several gram negative pathogens by controlling expression of pillin genes, regulation of differentiation by Caulobacter, and control of expression of xylose degredation genes and carboxypeptidase G2 in Pseudomonas.