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)，中枢神经系统己糖一磷酸分流途径的一种酶 中间代谢。6PGD水平受细胞因子的调节 增长速度，随着增长速度的增加增加了四倍。虽然这件事 变异在数量上类似于观察到的rRNA和r-蛋白， 我们未发表的关于营养变化和营养影响的实验结果 氨基酸饥饿对6PGD合成速率的影响 6PGD合成的生长速度控制机制与6PGD合成的控制机制不同 调节rRNA和r-蛋白的合成，是调节 许多其他蛋白质。 本提案的目的是阐明潜在的机制 6PGD合成的生长速率依赖性控制。几个型号的 提出了GND的规则，并将其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，使用我们以前分离的GND：：MUTS突变体。 这些融合将被用来确定依赖增长率的控制是否 6PGD的合成是转录或转录后的，并用于分离 具有GND突变或与GND不连锁的突变会改变生长速度的突变 控制力。GND控制区的DNA序列将被确定为野生的 鼠伤寒沙门氏菌的类型和突变基因以及GND，显示出一种 改变了生长速度的反应。S30提取物将从野生型中制备 细胞以不同的速度生长和来自突变体，并用于DNA依赖的 用于鉴定和表征生长速度调节剂的体外系统 6PGD合成的依赖调控。

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 Although this variation quantitatively resembles that observed for rRNA and r-proteins, results of our unpublished experiments on the effects of nutritional shifts and amino acid starvation on the rate of 6PGD synthesis demonstrated that the mechanism for growth rate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.