Controls on the Biosynthesis of Superoxide Dismutases in E. coli: An Inactive Precursor

大肠杆菌中超氧化物歧化酶生物合成的控制：一种无活性前体

• 批准号: 8809475
• 负责人: Irwin Fridovich
• 金额: $ 18万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-09-01 至 1992-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8809475&HistoricalAwards=false
• 关键词: Controls; Biosynthesis; Superoxide; Dismutases; E.

Escherichia coli can produce two types of superoxide dismutases. One of these, the iron enzyme is found in both aerobic and anaerobic cultures; while the second, a manganese enzyme, is ordinarily present only in aerobic cultures and can be strongly induced by hyperoxia, or by viologens and quinones which mediate intracellular production of O2-. The manner in which the cell controls the biosynthesis of the manganese enzyme has been under study but is not yet understood. This lab has reported that addition of an electron sink, such as paraquat plus nitrate, to an anaerobic culture causes production of the manganese enzyme in a form which is not active but which can be activated by addition of Mn(II) under mildly denaturing conditions; followed by removal of the denaturing stress. This is referred to as the pro-enzyme. It has also been shown that anaerobic cells contain another protein which is recognized by an antibody specific for the manganese enzyme, but which cannot be activated as can the pro-enzyme. This protein is referred to this as the prepro-enzyme. Experiments are being conducted to isolate, characterize and study the interconversions of these forms of the manganese-containing superoxide dismutase of E. coli.%%% Superoxide dismutases (SODs) are enzymes that provide defenses against the toxicity of molecular oxygen in living cells. It also protects against other stresses, e.g., ultra- violet radiation and sulfur dioxide exposure. How these enzymes are made is incompletely understood but important. The biosynthesis is probably regulated by environmental factors. This project will elucidate the pathway of enzyme synthesis and activation.***//

大肠杆菌可以产生两种类型的超氧化物歧化酶。 其中之一是铁酶，在需氧和厌氧培养物中均存在。第二种是锰酶，通常只存在于需氧培养物中，并且可以被高氧或介导细胞内产生 O2- 的紫精和醌强烈诱导。 细胞控制锰酶生物合成的方式已在研究中，但尚不清楚。 该实验室报告称，在厌氧培养物中添加电子汇（例如百草枯加硝酸盐）会导致产生锰酶，这种酶不具有活性，但可以通过在轻度变性条件下添加 Mn(II) 来激活；然后去除变性应力。 这被称为酶原。 研究还表明，厌氧细胞含有另一种蛋白质，该蛋白质可以被锰酶特异性抗体识别，但不能像酶原那样被激活。 这种蛋白质被称为前酶原。 正在进行实验来分离、表征和研究这些形式的大肠杆菌含锰超氧化物歧化酶的相互转化。%%%超氧化物歧化酶 (SOD) 是在活细胞中提供防御分子氧毒性的酶。 它还可以防止其他压力，例如紫外线辐射和二氧化硫暴露。 这些酶是如何制造的尚不完全清楚，但很重要。 生物合成可能受到环境因素的调节。 该项目将阐明酶合成和激活的途径。***//