title: A novel aspect of the inhibition by arsenicals of binding-protein-dependent galactose transport in gram-negative bacteria.
abstract: The inhibitory effects of arsenate and arsenite on binding-protein-dependent transport systems are reconsidered. It is shown that arsenate inhibits binding-protein-dependent galactose transport in proteoliposomes energized either by dihydrolipoamide and NAD+ or by a membrane potential (under conditions where ATP metabolism is not implicated); this result is in contradiction with the current interpretation of arsenate inhibition of binding-protein-dependent transport systems (which is based on ATP depletion) and can be explained by reference to the recently discovered ATP inhibition of the binding-protein-dependent galactose transport. In whole cells, the greater inhibition by arsenate of lipoamide-dependent transport than of protonmotive-force-dependent transport may be explained by a modification by arsenate of the pools of several compounds metabolized by 2-oxo-acid dehydrogenases (which have been implicated in binding-protein-dependent transport). The inhibition of binding-protein-dependent galactose transport by arsenite is probably linked to the inhibition by arsenite of the galactose-stimulated lipoamide dehydrogenase activity implicated in this transport and is reminiscent of the known arsenite inhibition of lipoamide dehydrogenases.
mesh_terms: D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D000255:Adenosine Triphosphate / Q000378:metabolism; D001149:Arsenates / Q000494:pharmacology*; D001151:Arsenic / Q000494:pharmacology*; D018053:Arsenites; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D003864:Depression, Chemical; D008058:Dihydrolipoamide Dehydrogenase / Q000037:antagonists & inhibitors; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism*; D005690:Galactose / Q000378:metabolism*; D007658:Ketone Oxidoreductases / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism; D012486:Salmonella typhimurium / Q000187:drug effects / Q000378:metabolism*
chemical_list: D001149:Arsenates; D018053:Arsenites; D002352:Carrier Proteins; D008081:Liposomes; D009097:Multienzyme Complexes; D000255:Adenosine Triphosphate; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D008058:Dihydrolipoamide Dehydrogenase; C015001:arsenite; D001151:Arsenic; D005690:Galactose