title: Accumulation of arsenate, phosphate, and aspartate by Sreptococcus faecalis.
abstract: Uptake of arsenate and phosphate by Streptococcus faecalis 9790 is strictly dependent on concurrent energy metabolism and essentially unidirectional. targinine supports uptake only in presence of glycerol or related substances; glycerol is not directly involved in transport but depletes the cellular orthophosphate pool and thus relieves feedback inhibition of transport. Uptake of phosphate and arsenate is stimulated by K+ and by other permeant cations. The results suggest that electroneutrality is preserved by compensatory movement of either H+ or OH minus. Ionophores and N,N'-dicyclohexylcarbodiimide, which prevent establishment of a proton motive force, block the accumulation of thiomethylgalactoside and of threonine but not that of arsenate or phosphate. We conclude that arsenate accumulation requires adenosine 5'-triphosphate but is not driven by the proton-motive force. However, conditions and reagents that lower the cytoplasmic pH do inhibit accumulation of arsenate and phosphate, suggesting that uptake depends on the capacity of the cells to maintain a neutral or alkaline cytoplasm. We therefore propose that phosphate accumulation is an electroneutral exchange for OH driven by adenosine 5'-triphosphate or by a metabolite thereof. Accumulation of aspartate and glutamate also requires adenosine 5'-triphosphate but not the proton-motive force and may involve a similar mechanism.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001120:Arginine / Q000378:metabolism; D001149:Arsenates / Q000378:metabolism*; D001151:Arsenic / Q000378:metabolism*; D001224:Aspartic Acid / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004734:Energy Metabolism; D013293:Enterococcus faecalis / Q000378:metabolism*; D005690:Galactose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000494:pharmacology; D006096:Gramicidin / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007461:Iodoacetates / Q000494:pharmacology; D008954:Models, Biological; D010710:Phosphates / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology
chemical_list: D001149:Arsenates; D007461:Iodoacetates; D010710:Phosphates; D006096:Gramicidin; D001224:Aspartic Acid; D004024:Dicyclohexylcarbodiimide; D000255:Adenosine Triphosphate; D001120:Arginine; D005947:Glucose; D001151:Arsenic; D005990:Glycerol; D011188:Potassium; D005690:Galactose