Baker H V, Wolf R E
J Bacteriol. 1983 Feb;153(2):771-81. doi: 10.1128/jb.153.2.771-781.1983.
The level of 6-phosphogluconate dehydrogenase is positively correlated with the cellular growth rate. To determine whether growth rate-dependent regulation of expression of gnd, which encodes this enzyme, is carried out by a transcriptional mechanism, the structural genes of the lactose operon were fused to and brought under the control of the gnd promoter through the use of phage Mu d1(Apr lac). Four independent gnd::Mu d1(Apr lac) operon fusion strains were isolated. After the Mu d1 prophage was replaced with lambda p1(209), Lac+ specialized transducing phages carrying the gnd-lac fusions were prepared. These phages were used to demonstrate that the lac genes were fused to the gnd promoter by crossing them with gnd promoter deletion mutants and with polar phage Mu cts-induced gnd mutants. A genetic map of the fusion joints was deduced. The level of beta-galactosidase in each fusion strain was the same in cells growing on acetate as in cells growing on glucose (with specific growth rate constants of 0.1 and 0.55 h-1, respectively) and was unaffected by the presence of a gnd+ gene in trans. Our results suggest that a post-transcriptional mechanism mediates growth rate-dependent regulation of gnd and that this regulation is not autogenous. Models for regulation are discussed with respect to these results and the physiology and DNA sequence of gnd.
6-磷酸葡萄糖酸脱氢酶的水平与细胞生长速率呈正相关。为了确定编码该酶的gnd基因的表达是否通过转录机制进行生长速率依赖性调控，利用噬菌体Mu d1(Apr lac)将乳糖操纵子的结构基因与gnd启动子融合并置于其控制之下。分离出四个独立的gnd::Mu d1(Apr lac)操纵子融合菌株。在用λ p1(209)替换Mu d1原噬菌体后，制备了携带gnd-lac融合的Lac⁺特异性转导噬菌体。通过将这些噬菌体与gnd启动子缺失突变体和极性噬菌体Mu cts诱导的gnd突变体杂交，证明了lac基因与gnd启动子融合。推导了融合接头的遗传图谱。在以乙酸盐为碳源生长的细胞和以葡萄糖为碳源生长的细胞中（比生长速率常数分别为0.1和0.55 h⁻¹），每个融合菌株中β-半乳糖苷酶的水平相同，并且不受反式存在的gnd⁺基因的影响。我们的结果表明，转录后机制介导了gnd的生长速率依赖性调控，并且这种调控不是自体的。针对这些结果以及gnd的生理学和DNA序列讨论了调控模型。
