Kilstrup M, Meng L M, Neuhard J, Nygaard P
Institute of Biological Chemistry B, University of Copenhagen, Denmark.
J Bacteriol. 1989 Apr;171(4):2124-7. doi: 10.1128/jb.171.4.2124-2127.1989.
Addition of purines to the growth medium of Escherichia coli represses synthesis of cytosine deaminase (codA) and enzymes of purine de novo synthesis. After Tn10 mutagenesis, mutants displaying derepressed levels of cytosine deaminase in the presence of hypoxanthine were isolated. One of these had simultaneously acquired resistance to the hypoxanthine analog 6-mercaptopurine. The mutation purR6::Tn10 was shown to affect de novo synthesis of the purine enzymes glutamine phosphoribosylpyrophosphate amidotransferase (purF) and phosphoribosyl glycinamide synthetase (purD). The mutation was mapped by P1 transduction at 36 min on the E. coli linkage map. A plasmid containing the purR region was obtained by complementation of the purR6::Tn10 mutation. By comparing the restriction maps of the cloned fragment and the E. coli chromosome, the purR gene was found to be located very close to the lpp gene (36.3 min).
向大肠杆菌的生长培养基中添加嘌呤会抑制胞嘧啶脱氨酶（codA）和嘌呤从头合成酶的合成。经Tn10诱变后，分离出了在次黄嘌呤存在下胞嘧啶脱氨酶水平去阻遏的突变体。其中一个突变体同时获得了对次黄嘌呤类似物6-巯基嘌呤的抗性。已证明突变purR6::Tn10会影响嘌呤酶谷氨酰胺磷酸核糖焦磷酸酰胺转移酶（purF）和磷酸核糖甘氨酰胺合成酶（purD）的从头合成。通过P1转导将该突变定位在大肠杆菌连锁图谱的36分钟处。通过对purR6::Tn10突变的互补作用获得了一个含有purR区域的质粒。通过比较克隆片段和大肠杆菌染色体的限制性图谱，发现purR基因非常靠近lpp基因（36.3分钟）。
