Transcription attenuation is the major mechanism by which the leu operon of Salmonella typhimurium is controlled

摘要: Abstract Three mutations, each causing constitutive expression of the Salmonella typhimurium leu operon, were cloned into phage vector λgt4 on EcoRI DNA fragments carrying all that operon except for part promoter-distal last gene. Sequence analysis from these demonstrated contains a single base change in attenuator. Transcription mutant vitro resulted transcription beyond usual site termination. The level β-IPM dehydrogenase, leuB enzyme, was elevated 40-fold strain one and starvation this leucine had little effect amount activity expressed. Using with wild-type promoter-leader region rates synthesis degradation leader RNA readthrough (leu mRNA) measured by DNA-RNA hybridizations specific probes. rate about same cells grown excess or limiting leucine. On other hand, mRNA 12-fold higher as opposed to species under both conditions growth. Thus, variation observed minimal medium is, most part, not caused control over frequency initiation differential stability species. Rather, is direct result termination at an attenuator site. These results taken together suggest attenuation major mechanism which regulates S. growing medium.