PHOSPHATE EFFLUX THROUGH THE CHANNELS FORMED BY COLICINS AND PHAGE T5IN ESCHERICHIA-COLI-CELLS IS RESPONSIBLE FOR THE FALL IN CYTOPLASMIC ATP

Previous studies have shown that channel formation in the cytoplasmic membrane of Escherichia coli by colicin A and phage T5 leads to an eff lux of cytoplasmic potassium and to a membrane depolarization. Here we show that upon opening of these channels, the intracellular ATP conce ntration is decreased to 10% of its original value in <5 min. ATP is n ot found in the external medium, but is hydrolyzed in the cytoplasm in to ADP and AMP. The rate of ATP hydrolysis depends on the number of ch annels and on their activity. ATP hydrolysis takes place if the F1F0-A TPase is absent or inhibited. Depolarization of the inner membrane is not the main cause of ATP hydrolysis. Opening of the phage and colicin channels also leads to an efflux of inorganic phosphate. Conditions t hat prevent the efflux of phosphate (i.e. depolarization of the cells and high external phosphate concentration) prevent ATP hydrolysis. We propose that ATP is hydrolyzed as a consequence of a shift in the ATP equilibrium due to the efflux of phosphate through the channels. The c onsequences for the cells of this ATP depletion are discussed.