Dover S, Halpern Y S
J Bacteriol. 1974 Feb;117(2):494-501. doi: 10.1128/jb.117.2.494-501.1974.
The control mutation that results in a concomitant severalfold increase in the activities of gamma-aminobutyrate-alpha-ketoglutarate transaminase (GSST, EC 2.6.1.19) and succinic semialdehyde dehydrogenase (SSDH, EC 1.2.1.16), leading to the acquisition of the ability to utilize gamma-aminobutyrate (GABA) as the sole source of nitrogen by Escherichia coli K-12 mutants, was mapped by mating and transduction with P1kc. The locus affected, gabC, is approximately 48% co-transduced with the thyA gene, located at min 55 of the E. coli K-12 chromosome. The structural gene of the first enzyme in the GABA pathway, GSST, was mapped by interrupted mating, using one of the GSST-less mutants, DB742, isolated in this work. The mutated locus, gabT, is situated at about min 73 of the E. coli chromosome, close to the gltC gene. Genetic evidence concerning the sensitivity of the enzymes of the GABA pathway to catabolite repression under different physiological conditions suggests that the two structural genes of the GABA regulon do not constitute one operon.
导致γ-氨基丁酸-α-酮戊二酸转氨酶（GSST，EC 2.6.1.19）和琥珀酸半醛脱氢酶（SSDH，EC 1.2.1.16）活性伴随性增加几倍的控制突变，使大肠杆菌K-12突变体获得了将γ-氨基丁酸（GABA）作为唯一氮源利用的能力，通过与P1kc进行交配和转导对其进行了定位。受影响的基因座gabC与位于大肠杆菌K-12染色体55分钟处的thyA基因共转导约48%。利用在本研究中分离得到的一个缺乏GSST的突变体DB742，通过中断交配对GABA途径中第一种酶的结构基因GSST进行了定位。突变基因座gabT位于大肠杆菌染色体约73分钟处，靠近gltC基因。关于GABA途径的酶在不同生理条件下对分解代谢物阻遏的敏感性的遗传证据表明，GABA调节子的两个结构基因不构成一个操纵子。
