Kimura M, Miki T, Hiraga S, Nagata T, Yura T
J Bacteriol. 1979 Dec;140(3):825-34. doi: 10.1128/jb.140.3.825-834.1979.
Three amber mutations, dna-801, dna-803, and dna-806, were isolated by localized mutagenesis of the dnaA-oriC region of the chromosome from an Escherichia coli strain carrying temperature-sensitive amber suppressors. When the mutations were not suppressed at 42 degrees C, the cells did not grow and DNA synthesis was arrested. They were very closely linked to each other and to the dnaA46 mutation. The mutant phenotype of each strain was converted to the wild type by infecting the mutants with specialized transducing phase lambda i21 dnaA-2 but not with lambda i21 tna. Derivatives of lambda i21 dnaA-2, each of which carried the amber mutation dna-801 dna-803, or dna-806, converted the dnaA mutant phenotype to Dna+ but did not convert rhe amber mutants to the wild-type phenotype. E. coli uvrB cells were irradiated with ultraviolet light and infected with each of these phage strains. An analysis of proteins synthesized in the cells revealed that two proteins with molecular weights of 50,000 and 43,000 were specified by lambda i21 dnaA-2 but not by lambda i21 tna. When the ultraviolet-irradiated cells did not carry an amber suppressor, the derivative phage with the amber mutation invariably failed to produce the 43,000-dalton protein, but when the host cell carried supF (tyrT), the protein was produced. The 50,000-dalton protein was unaffected.
通过对携带温度敏感型琥珀突变抑制基因的大肠杆菌菌株染色体的dnaA - oriC区域进行定位诱变，分离出了三个琥珀突变体，即dna - 801、dna - 803和dna - 806。当这些突变在42℃时未被抑制时，细胞无法生长且DNA合成停止。它们彼此之间以及与dnaA46突变紧密连锁。通过用特异性转导噬菌体λi21 dnaA - 2感染这些突变体，每个菌株的突变表型可转变为野生型，但用λi21 tna感染则不行。λi21 dnaA - 2的衍生物，每个都携带琥珀突变dna - 801、dna - 803或dna - 806，可将dnaA突变表型转变为Dna + ，但不能将琥珀突变体转变为野生型表型。用紫外线照射大肠杆菌uvrB细胞，然后用这些噬菌体菌株中的每一种进行感染。对细胞中合成的蛋白质进行分析发现，λi21 dnaA - 2可产生两种分子量分别为50,000和43,000的蛋白质，而λi21 tna则不能。当紫外线照射的细胞不携带琥珀突变抑制基因时，带有琥珀突变的衍生噬菌体总是无法产生43,000道尔顿的蛋白质，但当宿主细胞携带supF(tyrT)时，则会产生该蛋白质。50,000道尔顿的蛋白质不受影响。
