Multiple Mechanisms Are Used for Growth Rate and Stringent Control of leuV Transcriptional Initiation inEscherichia coli

摘要: The tRNA multigene family of Escherichia coli consists 84 structural genes, which produce 46 species (9). production is closely regulated such that under various physiological conditions the amount produced optimal for protein synthesis (16). It has become apparent use synonymous codons a given amino acid not random but strongly biased so codon chosen precisely correlated with relative abundance respective among isoacceptors. This particularly true highly expressed while, in weakly recognized by rare are used appreciable frequency. therefore important and interesting to understand factors ensure cellular complement anticodons all conditions. Earlier estimates showed as growth rate (expressed doublings per hour) increases from 0.6 2.5, concentration 6.3 × 104 7 105 molecules cell (10), been referred growth-rate-dependent control (GRDC). A recent study demonstrated numerous GRDC factor inversion stimulation (FIS) required regulation several (35). When inhibited E. starvation or analogues, synthesis, like rRNA curtailed level guanosine 3′,5′-bisdiphosphate (ppGpp) dramatically increased. response stringent response. Analyses individual suggest most if subject (SC) (7, 26, 43). proposed both SC modulated intracellular ppGpp, this remains controversial since it previously reported promoters appear display activity cells cannot synthesize ppGpp (19). seems clear number studies absolutely (12, 13, 19, 22–24). Added complexities genes have emerged these show some form feedback inhibition, perhaps involving ribosomes interact them (20, 21). Other data were interpreted be conflict idea presented (3). Vogel et al. when pyrBI strain was exposed partial pyrimidine starvation, levels directly rates (44). In addition, postinitiation effects may an and/or (45). shown clearly affects RNA polymerase elongation vivo vitro (28, 29, 46). Yet another rrn recently (18). at least two (rrnBp1 rrnDp1) require relatively high initiating nucleotide triphosphates (NTPs) unstable open complexes stabilized concentrations NTPs. promoter increased function NTP vitro. view results, rrnp1 well homeostatic ribosomal might explained (18). The leuV operon located 98 min genome three tRNA1Leu transcribed. our previous studies, we (leuVp) shares features promoters. First, contains upstream activating sequences (UAS) element (UP) (7). FIS appears bind UAS (39). We also core lacking UP displays flank (15). In study, attempted determine extent mechanisms employed genes. wished shared well-studied particular, examined putative role promoter. report here differences rrnBp1 regard multiple expression gene.