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  • Title: [Role of spot gene product in the degradation of pppGpp in bacteria].
    Author: Belitskiĭ BR, Shakulov RS.
    Journal: Mol Biol (Mosk); 1982; 16(4):857-64. PubMed ID: 6811860.
    Abstract:
    In Baccillus subtilis cells, in contrast to Escherichia coli cells, chelating agent 1,10-phenanthroline induces the expansion of guanosine-5'-diphosphate,3'-diphosphate( (ppGpp) pool, as well as the pool of its precursor guanosine-5'-triphosphate,3'-diphosphate (pppGpp). Under these conditions the degradation rate of both nucleotides decreases greatly, which is the main cause of their accumulation in the cells. In E. coli phenanthroline inactivates the product of spoT gene, which is responsible for ppGpp degradation, as a result of combining Mn2+ ions necessary for the activity of this enzyme. The addition of Mn2+ ions to B. subtilis cells, treated with phenanthroline, leads to the decline in (p)ppGpp pools. Antibiotic tetracycline, which has the chelating properties at the concentration of 1 mg/ml, also inactivates spoT gene product in E. coli and slows down the decay of ppGpp, but not of pppGpp. The addition of high concentrations of tetracycline to B. subtilis cells leads to severe inhibition of the degradation of both nucleotides. Therefore in B. subtilis spoT gene product is involved in the degradation of pppGpp, as well as ppGpp. In E. coli cells with defective gpp gene product, taking part in the conversion of pppGpp to ppGpp, phenanthroline and tetracycline also inhibit the breakdown of both nucleotides. The similarity of B. subtilis and E. coli gpp cells in respect of spoT gene product functions and of enhanced pppGpp fraction in the total amount of guanosine polyphosphates during aminoacyl-tRNA limitation makes it plausible that in B. subtilis cells the product of gpp gene is missing or has low activity.
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