Istúriz T, Palmero E, Vitelli-Flores J
J Gen Microbiol. 1986 Nov;132(11):3209-19. doi: 10.1099/00221287-132-11-3209.
An Escherichia coli strain unable to use gluconate was isolated by spontaneous curing of lambda cI857 s7 xis6 b515 b519, lambda cI857 s7 delta(A-att) dargI valS lysogens. Two lesions, linked to asd and pyrB markers, respectively, were necessary to produce this phenotype. The asd-linked mutation gnt-17, of regulatory type, seems to affect the expression of the major system of gluconate utilization (min 75) as well as that of 6-phosphogluconate dehydratase (gene edd, min 41), the first enzyme of the Entner-Doudoroff pathway. A closely linked suppressor of gnt-17 causes constitutivity of these activities; this suppressor resembles gntR, which is also in the asd region. Hence, it is possible that gnt-17 is a super-repressing allele of gntR, rather than a positive controlling element. Lesion gnt-17 alone does not prevent the utilization of gluconate; for this, the mutation gnt-18 at 96.9 min is also necessary. This mutation abolishes the thermosensitive gluconokinase activity and thus eliminates the subsidiary ability to catabolize gluconate. Accordingly, gnt-18 seems to be allelic with gntV, the locus postulated as being in the pyrB region specifying the thermosensitive gluconokinase.
通过对λcI857 s7 xis6 b515 b519、λcI857 s7 delta(A-att) dargI valS溶原菌进行自发治愈，分离出了一株无法利用葡萄糖酸盐的大肠杆菌菌株。分别与asd和pyrB标记相关的两个损伤是产生这种表型所必需的。与asd相关的调节型突变gnt-17似乎影响葡萄糖酸盐利用主要系统（75分钟区域）以及6-磷酸葡萄糖酸脱水酶（edd基因，41分钟区域）的表达，后者是Entner-Doudoroff途径的第一种酶。gnt-17的一个紧密连锁的抑制子导致这些活性组成型表达；这个抑制子类似于也在asd区域的gntR。因此，有可能gnt-17是gntR的一个超抑制等位基因，而不是一个正调控元件。单独的损伤gnt-17并不阻止葡萄糖酸盐的利用；为此，96.9分钟处的突变gnt-18也是必需的。这个突变消除了热敏性葡萄糖激酶活性，从而消除了分解代谢葡萄糖酸盐的辅助能力。因此，gnt-18似乎与gntV等位，gntV位点被推测位于pyrB区域，负责指定热敏性葡萄糖激酶。
