Calhoun M W, Gennis R B
School of Chemical Sciences, University of Illinois, Urbana 61801.
J Bacteriol. 1993 May;175(10):3013-9. doi: 10.1128/jb.175.10.3013-3019.1993.
The nature of the Escherichia coli membrane-bound NADH dehydrogenases and their role in the generation of the proton motive force has been controversial. One E. coli NADH:ubiquinone oxidoreductase has previously been purified to homogeneity, and its corresponding gene (ndh) has been isolated. However, two biochemically distinct E. coli NADH:ubiquinone oxidoreductase activities have been identified by others (K. Matsushita, T. Ohnishi, and H. R. Kaback, Biochemistry 26:7732-7737, 1987). An insertional mutation in the ndh gene has been introduced into the E. coli chromosome, and the resulting strain maintains membrane-bound NADH dehydrogenase activity, demonstrating that a second genetically distinct NADH dehydrogenase must be present. By standard genetic mapping techniques, the map position of a second locus (nuo) involved in the oxidation of NADH has been determined. The enzyme encoded by this locus probably translocates protons across the inner membrane, contributing to the proton motive force.
大肠杆菌膜结合NADH脱氢酶的性质及其在质子动力产生中的作用一直存在争议。一种大肠杆菌NADH：泛醌氧化还原酶此前已被纯化至同质，其相应基因（ndh）也已被分离。然而，其他人（K. 松下、T. 大西和H. R. 卡巴克，《生物化学》26：7732 - 7737，1987）已鉴定出两种生化性质不同的大肠杆菌NADH：泛醌氧化还原酶活性。已将ndh基因中的插入突变引入大肠杆菌染色体，所得菌株保持膜结合NADH脱氢酶活性，这表明必定存在第二种基因上不同的NADH脱氢酶。通过标准遗传图谱技术，已确定了参与NADH氧化的第二个位点（nuo）的图谱位置。该位点编码的酶可能使质子跨内膜转运，从而产生质子动力。
