Young I G, Wallace B J
Biochim Biophys Acta. 1976 Dec 6;449(3):376-85. doi: 10.1016/0005-2728(76)90149-3.
A strain carrying a point mutation affecting the NADH dehydrogenase complex of Escherichia coli has been isolated and its properties examined. The gene carrying the mutation (designated ndh) was located on the E. coli chromosome at about minute 23 and was shown to be cotransducible with the pyrC gene. Strain carrying the ndh- allele were found to be unable to grow on mannitol and to grow very poorly on glucose unless the medium was supplemented with succinate, acetate or casamino acids. The following properties of strains carrying the ndh- allele were established which suggest that the mutation affects the NADH dehydrogenase complex but apparently not the primary dehydrogenase. Membrane preparations possess normal to elevated levels of D-lactate oxidase and succinate oxidase activities but NADH oxidase is absent. NADH is unable to reduce ubiquinone in the aerobic steady state and reduces cytochrome b very slowly when the membranes become anaerobic. NADH dehydrogenase, measured as NADH-dichlorophenolindophenol reductase is reduced but not absent. NADH oxidase is stimulated by menadione although not by Q-3 or MK-1 and in the presence of menadione, cytochrome b is reduced normally by NADH. Further mutants affected in NADH oxidase were isolated using a screening procedure based on the growth characteristics of the original ndh- strain. The mutantions carried by these strains were all cotransducible with the pyrC gene and the biochemical properties of the additional mutants were similar to those of the original mutant. The properties of the group of ndh- mutants established so far suggest that they are affected in the transfer of reducing equivalents from the NADH dehydrogenase complex to ubiquinone.
已分离出一株携带影响大肠杆菌NADH脱氢酶复合体的点突变的菌株，并对其特性进行了研究。携带该突变的基因（命名为ndh）位于大肠杆菌染色体上约23分钟处，且显示与pyrC基因共转导。发现携带ndh-等位基因的菌株无法在甘露醇上生长，在葡萄糖上生长也非常差，除非培养基中添加琥珀酸盐、乙酸盐或酪蛋白氨基酸。确定了携带ndh-等位基因菌株的以下特性，这表明该突变影响NADH脱氢酶复合体，但显然不影响初级脱氢酶。膜制剂中D-乳酸氧化酶和琥珀酸氧化酶活性水平正常或升高，但不存在NADH氧化酶。在需氧稳定状态下，NADH无法还原泛醌，当膜变为厌氧状态时，NADH还原细胞色素b的速度非常慢。以NADH-二氯酚靛酚还原酶来衡量的NADH脱氢酶活性降低但并未缺失。甲萘醌可刺激NADH氧化酶，而Q-3或MK-1则不能，并且在存在甲萘醌的情况下，NADH可正常还原细胞色素b。利用基于原始ndh-菌株生长特性的筛选程序，分离出了更多影响NADH氧化酶的突变体。这些菌株携带的突变均与pyrC基因共转导，且其他突变体的生化特性与原始突变体相似。目前已确定的ndh-突变体组的特性表明，它们在将还原当量从NADH脱氢酶复合体转移至泛醌的过程中受到影响。
