GROWTH RATE-DEPENDENT CONTROL OF GENE EXPRESSION

大肠杆菌gnd基因编码6-磷酸葡萄糖酸脱氢酶 （6PGD），一种中枢神经系统己糖单磷酸分流途径的酶， 中间代谢 6 PGD的水平受细胞调节 增长率，随着增长率的增加而增加四倍。 虽然这 变化在数量上类似于对rRNA和r-蛋白质观察到的变化， 我们未发表的关于营养变化影响的实验结果， 氨基酸饥饿对6PGD合成速率的影响表明， 6PGD合成的生长速率控制机制不同于 调节rRNA和R蛋白的合成，并共同调节 许多其他蛋白质。 本提案的目的是阐明 6PGD合成的生长速率依赖性控制。 几种型号， gnd的规则，并作为设计的概念基础， 实验 将制备携带gnd-lac操纵子和基因融合的菌株 通过Casadaban的方法使用我们先前分离的gnd：：Mucts突变体。 融合体将用于确定是否生长速率依赖性控制 6PGD合成是转录的或转录后的，并且用于分离 gnd突变或与gnd不相关的突变体，其改变生长速率 控制 将确定野生型gnd控制区的DNA序列。 型和突变基因和gnd的鼠伤寒沙门氏菌，这表明， 改变生长速度反应。 S30提取物将从野生型中制备 细胞生长在不同的速度和从突变体，并用于DNA依赖的， 用于鉴定和表征生长速率调节剂的体外系统 6PGD合成的依赖性控制。

The gnd gene of Escherichia coli encodes 6-phosphogluconate dehydrogenase (6PGD), an enzyme of the hexose monophosphate shunt pathway of central intermediary metabolism. The levels of 6PGD are regulated by the cellular growth rate, increasing fourfold with increasing growth rate. Although this variation quantitatively resembles that observed for rRNA and r-proteins, results of our unpublished experiments on the effects of nutritional shifts and amino acid starvation on the rate of 6PGD synthesis demonstrated that the mechanism for growth rate control of 6PGD synthesis is distinct from that which regulates synthesis of rRNA and r-protein and is common to the regulation of many other proteins. The objective of the present proposal is to elucidate the mechanisms underlying the growth rate-dependent control of 6PGD synthesis. Several models for regulation of gnd are presented and used as a conceptual base for the design of experiments. Strains carrying gnd-lac operon and gene fusions will be prepared by the methods of Casadaban using our previously isolated gnd::Mucts mutants. The fusions will be used to determine whether growth rate-dependent control of 6PGD synthesis is transcriptional or post-transcriptional and for the isolation of mutants with mutations in gnd or unlinked to gnd which alter growth rate control. The DNA sequence of the gnd control region will be determined for wild type and mutant genes and for gnd of Salmonella typhimurium, which shows an altered growth rate response. S30 extracts will be prepared from wild type cells grown at different rates and from mutants, and used in DNA-dependent in vitro systems to identify and characterize the regulators of growth rate dependent control of 6PGD synthesis.