Searles L L, Jones J W, Fournier M J, Grambow N, Tyler B, Calvo J M
J Bacteriol. 1986 Apr;166(1):341-5. doi: 10.1128/jb.166.1.341-345.1986.
Escherichia coli B/r strain EB146 containing mutation leuK16 has elevated levels of enzymes involved in the synthesis of leucine, valine, isoleucine, histidine, and tryptophan (Brown et al., J. Bacteriol. 135:542-550, 1978). We show here that strain EB146 (leuK16) has properties that are similar to those of E. coli and Salmonella typhimurium hisT strains. In tRNA1Leu from both hisT and leuK strains, positions 39 and 41 are uridine residues rather than pseudouridine residues. Furthermore, in tRNA3Leu and tRNA4Leu from a leuK strain, uridine residues at positions 39 and 40, respectively, are unmodified. Pseudouridine synthase I activity is missing in extracts of strain EB146 (leuK16), and extracts of strain EB146 (leuK16) and of a hisT strain do not complement one another in vitro. Four phenotypes of strain EB146 (leuK16), leucine excretion, wrinkled colony morphology, and elevated levels of leu and his enzymes, are complemented by a plasmid having a 1.65-kilobase DNA fragment containing the E. coli K-12 hisT locus. These results indicate that either leuK codes for pseudouridine synthase I (and is thus a hisT locus in reality) or, less likely, it codes for a product that affects the synthesis or activity of pseudouridine synthase I.
含有leuK16突变的大肠杆菌B/r菌株EB146中，参与亮氨酸、缬氨酸、异亮氨酸、组氨酸和色氨酸合成的酶水平升高（Brown等人，《细菌学杂志》135:542 - 550，1978年）。我们在此表明，菌株EB146（leuK16）具有与大肠杆菌和鼠伤寒沙门氏菌hisT菌株相似的特性。在来自hisT和leuK菌株的tRNA1Leu中，第39位和第41位是尿苷残基而非假尿苷残基。此外，在来自leuK菌株的tRNA3Leu和tRNA4Leu中，第39位和第40位的尿苷残基未被修饰。菌株EB146（leuK16）的提取物中缺乏假尿苷合酶I活性，并且菌株EB146（leuK16）和hisT菌株的提取物在体外不能相互互补。菌株EB146（leuK16）的四种表型，即亮氨酸排泄、皱缩菌落形态以及leu和his酶水平升高，可被携带包含大肠杆菌K - 12 hisT基因座的1.65千碱基DNA片段的质粒互补。这些结果表明，要么leuK编码假尿苷合酶I（因此实际上是一个hisT基因座），要么可能性较小的是，它编码一种影响假尿苷合酶I合成或活性的产物。
