Anderson J J, Quay S C, Oxender D L
J Bacteriol. 1976 Apr;126(1):80-90. doi: 10.1128/jb.126.1.80-90.1976.
Two mutant loci resulting in derepression of, respectively, the L-leucine-specific transport system (lstR) and both the leucine-specific and the general branched-chain amino acid transport LIV-I systems (livR) were mapped by conjugation and transduction. Both livR and lstR were found to be closely linked to aroA at min 20 on the Escherichia coli genetic map. The merodiploid livR+/livR displayed wild-type regulation of L-leucine transport, indicating that the livR product is a diffusible, negative controlling element for high-affinity leucine transport systems. Isogenic strains carrying lstR, livR, and wild-type transport alleles were compared for leucine uptake kinetic parameters and leucine-binding protein levels. The higher levels of leucine transport in the mutant strains under repressing conditions were generally due to increased high-affinity systems, which were accompanied by striking increases in the level of leucine-binding proteins.
通过接合和转导定位了两个突变位点，分别导致L-亮氨酸特异性转运系统（lstR）以及亮氨酸特异性和通用支链氨基酸转运LIV-I系统（livR）的去阻遏。发现livR和lstR在大肠杆菌遗传图谱上的20分钟处均与aroA紧密连锁。部分二倍体livR+/livR显示出L-亮氨酸转运的野生型调控，表明livR产物是高亲和力亮氨酸转运系统的一种可扩散的负调控元件。比较了携带lstR、livR和野生型转运等位基因的同基因菌株的亮氨酸摄取动力学参数和亮氨酸结合蛋白水平。在阻遏条件下，突变菌株中较高水平的亮氨酸转运通常是由于高亲和力系统增加所致，同时亮氨酸结合蛋白水平也显著增加。
