Zambrano M M, Kolter R
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115.
J Bacteriol. 1993 Sep;175(17):5642-7. doi: 10.1128/jb.175.17.5642-5647.1993.
We have previously characterized mutant strains of Escherichia coli that are able to take over stationary-phase cultures. Here we describe two insertion mutations that prevent such strains from expressing this phenotype. Both insertions were mapped to min 51, and sequence analysis revealed that both mutated genes encode proteins homologous to subunits of mitochondrial NADH dehydrogenase I. Crude extracts prepared from both mutant strains were able to oxidize NADH but lacked the enzymatic activity needed to oxidize deamino-NADH, a substrate specific for NADH dehydrogenase I. This is the first identification of genes encoding subunits of NADH dehydrogenase I in E. coli. The significance of the inability of these mutant strains to compete in stationary-phase cultures is discussed.
我们之前已对能够接管稳定期培养物的大肠杆菌突变株进行了特征描述。在此，我们描述了两个插入突变，它们阻止了此类菌株表达该表型。两个插入位点均被定位到51分钟处，序列分析表明，这两个突变基因编码的蛋白质与线粒体NADH脱氢酶I的亚基同源。从这两个突变株制备的粗提取物能够氧化NADH，但缺乏氧化脱氨基NADH（NADH脱氢酶I的特异性底物）所需的酶活性。这是首次在大肠杆菌中鉴定出编码NADH脱氢酶I亚基的基因。我们还讨论了这些突变株在稳定期培养物中无法竞争的意义。
