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: 3297888
• 负责人: THOMAS EDWARD ELLIOTT
• 金额: $ 16.9万
• 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 1996-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3297888
• 关键词: 5 aminolevulinate synthase; Salmonella typhimurium; anaerobiosis; bacterial genetics; chimeric proteins; enteric bacteria; enzyme mechanism; fermentation; gene expression; genetic mapping; genetic promoter element; genetic regulation; genetic regulatory element; heme; immunoprecipitation; lac operon; microorganism metabolism; molecular cloning; mutant; nucleic acid sequence; porphyrin biosynthesis; radiotracer; starvation; superoxide dismutase

Heme serves Salmonella typhimurium as the cofactor both for cytochromes (required for respiration) and for catalase (involved in defense against oxygen's toxic effects). In S. typhimurium, the heme pathway also leads to siroheme and to vitamin B 12, which is an essential nutrient for humans. Surprisingly, very little is known about the regulation of this branched pathway in enteric bacteria. Since S. typhimurium well-suited to genetic analysis, we propose a primarily genetic approach to understanding the control of heme synthesis. We have been investigating the role of the hemA and hemL genes in the synthesis of ALA, the first committed, stable intermediate in the heme pathway. We have also identified a large number of hem mutants, and characterized the genes so defined. Here we concentrate on three specific systems chosen to illuminate different aspects of heme regulation. The hemA gene encodes the first enzyme specific to the heme pathway, glutamyl tRNA reductase. We are studying control of hemA gene expression during starvation for heme and in different growth conditions. We've also discovered a pair of genes, hemF and hemN, that encode alternative aerobic and anaerobic enzymes for a late step in heme synthesis, and we'll study the influence of oxygen on these genes. Finally, we've learned that S. typhimurium has two routes of ALA synthesis, and we suspect that this duality is important in regulating flow through the pathway to different end products. This study is also relevant to the larger problem of S. typhimurium's life in the colon. Most of what we know about enteric bacteria has been observed during growth in air. As a facultative anaerobe, S. typhimurium 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.

血红素将鼠伤寒沙门氏菌作为细胞色素的辅助因子 （呼吸需要）和过氧化氢酶（参与防御 氧气的毒性作用）。 在鼠伤寒链球菌中，血红素途径也导致 对Siroheme和维生素B 12，这是人类必不可少的营养。 令人惊讶的是，关于这个分支的调节知之甚少 肠道细菌的途径。 由于鼠伤寒链球菌非常适合遗传 分析，我们提出了一种理解的遗传学方法 血红素合成的控制。 我们一直在研究HEMA和HEML基因在 Ala的合成，Ala是血红素中的第一个投入，稳定的中间体 路径。 我们还确定了大量的下摆突变体，并且 表征了如此定义的基因。 在这里，我们专注于三个特定 被选为阐明血红素调节的不同方面的系统。 这 HEMA基因编码针对血红素途径的第一个酶 tRNA还原酶。 我们正在研究对Hema基因表达的控制 血红素和不同生长条件下的饥饿。 我们也有 发现了一对基因，Hemf和Hemn，编码替代有氧运动 和厌氧酶是血红素合成的晚期，我们将研究 氧对这些基因的影响。 最后，我们了解到S. 伤寒有两种ALA合成途径，我们怀疑这是 二元性对于调节通往不同途径的流动很重要 最终产品。 这项研究也与鼠伤寒沙门氏菌的更大问题有关 在结肠。 我们对肠细菌的了解的大多数是 在空气生长期间观察到。 作为辅助厌食症，孢子虫 当电子受体在场时呼吸，但也可以通过 在缺席的情况下发酵。 在本质上，电子受体可能是 仅凭间歇性（在饮食中或氧气从 上皮表面）。 快速发展呼吸道的能力 能力可能非常重要。 我们将尝试利用血红素法规 作为对控制基因功能控制基因功能的一种方法的方法 氧。