guanosine-triphosphate and methylglucoside

The accumulation of RNA and protein and the kinetics of nucleoside triphosphate and guanosine polyphosphate pools during amino acid starvation and carbon source downshift were investigated in Streptomyces hygroscopicus. RNA accumulation was controlled stringently during both amino acid starvation and carbon source downshift. The pool size of ppGpp increased dramatically under these conditions. However, the intracellular concentrations of nucleoside triphosphates were low and the concentration of guanosine polyphosphates was much lower than in Escherichia coli. The possible significance of this phenomenon in the regulation is discussed.

Topics: Adenosine Triphosphate; Amino Acids; Autoradiography; Bacterial Proteins; Guanosine Pentaphosphate; Guanosine Tetraphosphate; Guanosine Triphosphate; Methylglucosides; Methylglycosides; Nucleotides; RNA, Bacterial; Serine; Streptomyces

The uptake of the GTP analogue guanylyl(beta,gamma-methylene)diphosphonate (GppCH2p) is the same in Semliki Forest virus (SFV)-infected BHK cells as in mock-infected cells, in spite of the fact that protein synthesis is inhibited by GppCH2p more markedly in SFV-infected cells than in control cells. A possible explanation for this difference is that infected cells have a lower concentration of GTP and a lower ratio of GTP:GDP than uninfected cells, and the analogue may thus be a more effective competitive inhibitor of translation. We conclude that in this system, the difference between infected and uninfected cells lies not at the plasma membrane but within the cytoplasm.

Topics: Animals; Cell Line; Cell Membrane Permeability; Cricetinae; Diphosphonates; Guanine Nucleotides; Guanosine Monophosphate; Guanosine Triphosphate; Methylglucosides; Protein Biosynthesis; Semliki forest virus

Certain nucleotides control adaptation to changing nutrition or differentiation (sporulation) resulting from a general nutritional deficiency. To maintain the adaptation or differentiation process, once it has started, it may have been important for cells to evolve several independent and metabolically controllable systems enabling the uptake and metabolism of various nucleic acid bases or nucleosides. We have analyzed the cellular reactions with these compounds by measuring both their effect on growth and their uptake in appropriately chosen auxotrophic and uptake mutants. We have found one uptake system for guanine and hypoxanthine, another one for guanosine and inosine, and three other systems for adenine, adenosine, and uracil. The uptake systems of guanine-hypoxanthine and guanosine-inosine are inhibited by the stringent response to amino acid deprivation (increase of guanosine 5'-diphosphate-3'-diphosphate), but they do not depend on the concentration of GTP, which decreases during sporulation. In contrast, the uptake of Ura depends on the presence of GTP, regardless of whether a GTP decrease was produced by the stringent response or otherwise. This was the only uptake system whose decrease was always correlated with the onset of sporulation. The uptake of other compounds, e.g., alpha-methylglucoside and alpha-aminoisobutyric acid, decreased under some, but not all, sporulation conditions.

Topics: Adenine; Adenosine; Aminoisobutyric Acids; Bacillus subtilis; Biological Transport; Guanine; Guanosine; Guanosine Triphosphate; Hypoxanthine; Hypoxanthines; Inosine; Kinetics; Methylglucosides; Methylglycosides; Purines; Spores, Bacterial; Uracil