Abstract: | The effect of the accumulation of β-galactosides on the uptake of Pi into cells and cell nucleotides was examined in ML strains of Escherichia coli. Nonmetabolizable sulfur analogs of lactose, which are accumulated only in the presence of the product of y gene of the Lac operon, inhibited the uptake of P1 into whole cells and into cell nucleotides. This inhibition was most pronounced in starved cells, those with a low rate of ATP production. When the cell membrane was disrupted by sonication or detergents, the inhibition was lost. No significant inhibition was seen in y? strains or in inducible y+ strains which were not induced. Hence. inhibition of the uptake of phosphate into nucleotides is dependent on the presence of the product of the y gene and a β-galactoside.A technique using 32Pi and 33P1 was developed for simultaneously measuring the turnover and level of nucleotides. β-Galactosides inhibited ATP synthesis in aerobic cells, but stimulated ATP synthesis in anaerobic cells, indicating that an intermediate of oxidative phosphorylation was the source of energy for β-galactoside accumulation. |