title: Effect of arsenate on inorganic phosphate transport in Escherichia coli.
abstract: The effect of arsenate on strains dependent on the two major inorganic phosphate (Pi) transport systems in Escherichia coli was examined in cells grown in 1 mM phosphate medium. The development of arsenate-resistant Pi uptake in a strain dependent upon the Pst (phosphate specific transport) system was examined. The growth rate of Pst-dependent cells in arsenate-containing medium was a function of the arsenate-to-Pi ratio. Growth in arsenate-containing medium was not due to detoxification of the arsenate. Kinetic studies revealed that cells grown with a 10-fold excess of arsenate to Pi have almost a twofold increase in capacity (Vmax) for Pi, but maintained the same affinity (Km). Pi accumulation in the Pst-dependent strain was still sensitive to changes in the arsenate-to-Pi ratio, and a Ki (arsenate) for Pi transport of 39 microM arsenate was determined. The Pst-dependent strain did not accumulate radioactive arsenate, and showed only a transient decrease in intracellular adenosine triphosphate levels after arsenate was added to the medium. The Pi transport-dependent strain ceased growth in arsenate-containing media. This strain accumulated 74As-arsenate, and intracellular adenosine triphosphate pools were almost completely depleted after the addition of arsenate to the medium. Arsenate accumulation required a metabolizable energy source and was inhibited by N-ethylmaleimide. Previously accumulated arsenate could exchange with arsenate or Pi in the medium.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001149:Arsenates / Q000378:metabolism / Q000494:pharmacology*; D001151:Arsenic / Q000494:pharmacology*; D001693:Biological Transport, Active / Q000187:drug effects; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D010710:Phosphates / Q000378:metabolism*
chemical_list: D001149:Arsenates; D010710:Phosphates; D000255:Adenosine Triphosphate; D001151:Arsenic