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The nucleotides ppGpp and pppGpp accumulate when wild-type, but not rel(-), strains of Escherichia coli are starved for required amino acids. These compounds are synthesized on ribosomes, in the presence of the product of the rel gene, from GDP and GTP; ATP is used as the phosphate donor. The signal for making these compounds is the presence of an uncharged(More)
The stringent factor from Escherichia coli is the product of the relA locus. It is the enzyme that catalyzes the synthesis of pppGpp and ppGpp eliciting a pyrophosphate transfer from ATP to the 3'--OH of GTP (or GDP). This protein is responsible for the synthesis of pppGpp and ppGpp in stringent strains in response to an amino acid starvation. In vitro it(More)
  • L Eron, R Block
  • 1971
A cyclic AMP-binding protein (CAP protein), cyclic AMP, and RNA polymerase holoenzyme are shown to initiate lac transcription at the lac promoter. Lac repressor appears to control transcription by preventing RNA polymerase and/or CAP protein from binding to the lac promoter. Results support the idea that the lac promoter is composed of two sites that(More)
In this paper we present a brief look at some of the knowledge-based processes used in gener-atii~g referring expressions in the natural language advisory system WlSBER. Although WISBER is fully capable of exploiting syntactic information to generate contextually appropriate references, the work described here concentrates on the use of conceptual and(More)
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