GENETIC CONTROL OF HEME SYNTHESIS IN S. TYPHIMURIUM

鼠伤寒沙门氏菌血红素合成的基因控制

• 批准号: 3297891
• 负责人: THOMAS EDWARD ELLIOTT
• 金额: $ 10.17万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-07-01 至 1992-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3297891
• 关键词: 5 aminolevulinate synthase; Salmonella typhimurium; anaerobiosis; bacterial genetics; enteric bacteria; enzyme mechanism; gene expression; genetic mapping; genetic regulation; heme; molecular cloning; mutant; nucleic acid sequence; porphyrin biosynthesis; radiotracer; structural genes; superoxide dismutase

Heme serves Salmonella typhimurium as the cofactor both for cytochromes (required for respiration) and for catalase and superoxide dismutase (involved in defense against oxygen's toxic effects). In Salmonella, the heme pathway also leads to siroheme and to vitamin B12, which is an essential nutrient for humans. Surprisingly, very little is known about the regulation of this branched pathway in enteric bacteria. Since Salmonella is well- suited to genetic analysis, we propose a primarily genetic approach to understanding the control of heme synthesis. This study is also relevant to the larger problem of Salmonella's life in the colon. Most of what we know about enteric bacteria has been observed during growth in air. As a facultative anaerobe, Salmonella respires to electron acceptors when they are present, but can also grow by fermentation in their absence. In nature, electron acceptors may be present only intermittently (in the diet, or as oxygen diffusing from the epithelial surface). The ability for rapid development of respiratory capacity may be very important. We'll attempt to exploit heme regulation as an approach to more general questions about control of gene function by oxygen Our initial studies have focused on the first step of the pathway, synthesis of ALA. We've learned that Salmonella has two routes of ALA synthesis, and we suspect that this duality is important in regulating flow through the pathway to different end products. The major route of ALA synthesis (both aerobically and anaerobically) depends on the hemeA and hemL genes. We'll characterize these genes and their regulation, and study the enzyme, ALA synthase. The second route of ALA synthesis is expressed only anaerobically. It may be related to the C5 route of ALA synthesis used in photosynthetic organisms. We've isolated Mud-lac fusions to most of the genes of the heme pathway, and we'll use these select and characterize mutations regulating expression of heme genes. Having a set of well characterized hem mutants and simple methods for working with them also allow rapid molecular biological characterization of these genes and the heme pathway enzymes.

血红素将鼠伤寒沙门氏菌作为辅助因子 细胞色素（呼吸需要）和过氧化氢酶和 超氧化物歧化酶（参与抗氧有毒的防御 效果）。 在沙门氏菌中，血红素途径也导致Siroheme 以及维生素B12，这是人类必不可少的营养。 令人惊讶的是，对此的调节知之甚少 肠细菌中的分支途径。 由于沙门氏菌很好 适合遗传分析，我们提出了一个主要的遗传 理解血红素合成控制的方法。 这项研究也与沙门氏菌的更大问题有关 结肠的生活。 我们对肠细菌的了解的大多数 在空气生长过程中已经观察到。 作为教师 Anaerobe，沙门氏菌对电子受体的呼吸是 在场，但也可以在缺席的情况下通过发酵而生长。 在 自然，电子受体只能间歇地存在（在 饮食，或从上皮表面扩散的氧气）。 这 快速发展呼吸能力的能力可能非常 重要的。 我们将尝试将血红素调节作为一个 关于控制基因功能的更一般性问题的方法 通过氧气 我们的最初研究集中于途径的第一步， ALA的合成。 我们了解到沙门氏菌有两条路线 关于ALA合成的内容，我们怀疑这种双重性在 调节流经通往不同最终产品的途径的流动。 ALA合成的主要途径（有氧和 厌氧）取决于hemea和heml基因。 出色地 表征这些基因及其调节，并研究 酶，ALA合酶。 ALA合成的第二个途径是 仅厌氧表达。 它可能与C5路线有关 光合生物中使用的ALA合成。 我们已经 与血红素的大多数基因分离的泥唇融合 途径，我们将使用这些选择和表征突变 调节血红素基因的表达。 有一套井 表征下摆突变体和与之合作的简单方法 它们还允许快速的分子生物学表征 这些基因和血红素途径酶。