Urbanowski M L, Plamann L S, Stauffer G V
J Bacteriol. 1987 Jan;169(1):126-30. doi: 10.1128/jb.169.1.126-130.1987.
We isolated and characterized cis-acting mutations that affect the regulation of the metB gene of Salmonella typhimurium LT2. The mutations were isolated in an Escherichia coli lac deletion strain lysogenized with lambda bacteriophage carrying a metB-lacZ gene fusion (lambda JBlac) in which beta-galactosidase production is dependent upon metB gene expression. The mutant lysogens show elevated, poorly regulated beta-galactosidase production. The altered regulation is a result of disruption of the methionine control system mediated by the metJ repressor. The mutations are located in a region of dyad symmetry centered near the -35 sequence of the metB promoter. We propose that these mutations alter the repressor binding site and define the metB operator sequence. In addition, we discuss a highly conserved, nonsymmetric DNA sequence of unknown function which occurs in the control regions of the metA, metC, metE, metF, metG, and metJB genes of both S. typhimurium and E. coli.
我们分离并鉴定了影响鼠伤寒沙门氏菌LT2 metB基因调控的顺式作用突变。这些突变是在用携带metB - lacZ基因融合体（λJBlac）的λ噬菌体溶原化的大肠杆菌lac缺失菌株中分离得到的，其中β - 半乳糖苷酶的产生依赖于metB基因的表达。突变溶原菌显示出β - 半乳糖苷酶产量升高且调控不佳。这种调控改变是由metJ阻遏物介导的甲硫氨酸控制系统破坏所致。这些突变位于以metB启动子 - 35序列附近为中心的二元对称区域。我们提出这些突变改变了阻遏物结合位点并确定了metB操纵序列。此外，我们讨论了在鼠伤寒沙门氏菌和大肠杆菌的metA、metC、metE、metF、metG和metJB基因的控制区域中出现的一个功能未知的高度保守的非对称DNA序列。
