Synthesis and turnover of basal level guanosine tetraphosphate in Escherichia coli.
نویسندگان
چکیده
Cultures of escherichia coli growing exponentially in Trisacetate medium were subjected to nutritional shift-up and the pool size of guanosine 5'-3'-diphosphate-3'diphosphate (ppGpp) as well as the rates of protein synthesis and net RNA synthesis were determined. In the shift to a rich medium (glucose plus 19 amino acids plus hypoxanthine) the basal level of ppGpp falls immediately with a decay constant suggesting total inhibition of synthesis; ther is no ppGpp detectable above background for 30 to 40 min. The net rate of RNA synthesis starts to increase within 1 min of the shift-up and has reached its definite postshift value well before the pool of ppGGpp rises above background lvel. In a shift-up from Tris-acetate medium to Tris-glucose medium there is a much slower readjustment of the ppGpp pool size without the transient disappearance of the nucleotide. However, in a shift-up to Tris-acetate plus 5 amino acids, a medium which supports the same growth rate as Tris-glucose medium, a dramatic, transient drop in the ppGpp pool level was observed. Relaxed cells exhibit very similar behavior to strigent cells in the same shift-up. Our data argue strongly against an exclusive role for pGpp in regulating RNA synthesis during niutritional shift-up. The kinetic data of [3H]guanosine uptake into GTP and ppGpp pools were analyzed to determine the rate of pGpp synthesis. This rate was found to be similar during expotential growth in either Tris-acetate medium. During a shift-down from Tris-glucose to Tris-acetate medium the rate of ppGpp syntesis fell by a factor of 1.5 to 2 and the turnover rate is reduced 6- to 8-fold, suggesting that the expansion in the ppGp pool during shift-down canot be due to derepression of synthesis.
منابع مشابه
Correlation between RNA synthesis and basal level guanosine 5'-diphosphate 3'-diphosphate in relaxed mutants of Escherichia coli.
Through the use of a new nucleotide extraction procedure, we had previously shown that relaxed mutants of Escherichia coli exhibit a unique response to amino acid starvation (Lagosky, P. A., and Chang, F. N. (1980) J. Bacteriol. 144, 499-508). The basal level amounts of guanosine 5'-diphosphate 3'-diphosphate (ppGpp) in both relA and phenotypically relaxed relA+ rplK (relC) strains were shown t...
متن کاملSynthesis and Turnover of Basal Level Guauosine Tetraphosphate in Escherichia coZi*
Cultures of Escherichia coli growing exponentially in Trisacetate medium were subjected to nutritional shift-up and the pool size of guanosine 5’-diphosphate-3’-diphosphate (ppGpp) as well as the rates of protein synthesis and net RNA synthesis were determined. In the shift to a rich medium (glucose plus 19 amino acids plus hypoxanthine) the basal level of ppGpp falls immediately with a decay c...
متن کاملDifferent effects of ppGpp on Escherichia coli DNA replication in vivo and in vitro☆
Inhibition of Escherichia coli DNA replication by guanosine tetraphosphate (ppGpp) is demonstrated in vitro. This finding is compatible with impairment of the DnaG primase activity by this nucleotide. However, in agreement to previous reports, we were not able to detect a rapid inhibition of DNA synthesis in E. coli cells under the stringent control conditions, when intracellular ppGpp levels i...
متن کاملOn the regulation of guanosine tetraphosphate levels in stringent and relaxed strains of Escherichia coli.
We have examined the intracehular levels of the guanosine tetraphosphate, guanosine 5’-diphosphate 2’or 3’-diphosphate (ppGpp), in an isogenic pair of stringent and relaxed strains of Escherichia coli. As previously observed, relaxed strains do not accumulate ppGpp during amino acid deprivation, while stringent strains do. However, under all other culture conditions examined, relaxed and string...
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ورودعنوان ژورنال:
- The Journal of biological chemistry
دوره 250 1 شماره
صفحات -
تاریخ انتشار 1975