MODE OF ACTION OF A BACTERIAL FUNCTION INVOLVED IN CELL GROWTH CONTROL

我们一直在研究蛋白质降解在调节 通过对缺陷突变株的研究来控制细胞生长 依赖于ATP的蛋白质降解。大肠埃希氏菌离子突变体在 DNA损伤后的细胞分裂调控，我们之前已经 证明这一缺陷是由于高度不稳定的 细胞分裂抑制因子，是苏拉基因的产物。Lon变种人也 大量生产胶囊多糖，我们已经开发了一种系统，用于 囊膜合成所需基因调控的研究， 起诉cps：：lac操纵子融合。我们已经分离并绘制了基因突变图 调节囊膜合成的三个基因(RCSA、RCSB和RCSC)。全 已经克隆了三个调控基因，蛋白质产品正在进行 已确认身份。基因实验表明，存在一系列 调控相互作用调节cps转录 结构基因；未来的工作将允许在体外重建这个 调节级联反应和Lon在这一过程中的确切作用 系统。对缺乏离子活性的细胞的研究证实了 在大肠杆菌中的其他APT依赖的蛋白分解系统。我们将发展 这些其他蛋白酶基因突变的遗传选择，以及 这些活动的生化特征。此外，我们还有 演示了一种天然Lon底物的体外降解 Lambda N蛋白。对这种退化过程的进一步研究将使 Lon蛋白水解酶特性分析。

We have been studying the role that protein degradation plays in regulating cell growth control, through the study of mutants defective in ATP-dependent protein degradation. E. coli lon mutants are defective in cell division regulation after DNA damage, and we have previously demonstrated that this defect is due to stabilization of a highly unstable cell division inhibitor, the product of the SulA gene. lon mutants also overproduce capsular polysaccharide, and we have developed a system for the study of the regulation of the genes necessary for capsule synthesis (cps), suing cps::lac operon fusions. We have isolated and mapped mutations in three genes which regulate capsule synthesis (rcsA, rcsB, and rcsC). All three regulatory genes have been cloned, and the protein products are being identified. Genetic experiments indicated the existence of a cascade of regulatory interactions to regulate the transcription from the cps structural genes; future work will allow the in vitro reonstruction of this regulatory cascade andidentification of the precise role of lon in this system. Studies on cells devoid of lon activity demonstrate the existence of other APT-dependent proteolysis systems in E. coli. We will develop genetic selections for mutations in these other protease genes, as well as the biochemical characterization of these activities. In addition, we have demonstrated the in vitro degradation of a natural Lon substrate, the lambda N protein. Further studies of this degradation process will allow an analysis of the characteristics of Lon proteolysis.