title: A novel type of coupling between proline and galactoside transport in Escherichia coli.
abstract: Exit of thiomethylgalactoside (TMG) from preloaded cells induced the accumulation of proline. Likewise, proline exit stimulated TMG accumulation. Since a proton ionophore (carbonylcyanide-m-chlorophenylhydrazone) abolished these effects, a protonmotive force was implicated as the "intermediate" in the coupling reaction. The evidence suggests that the exit of TMG resulted in proton exit, which produced either a membrane potential (inside negative or a pH gradient (outside acid) or both. This inwardly directed protonmotive force provided the energy for proline entry and accumulation. Thus the energy coupling was not via a common transport protein but by proton movements which coupled the two separate H+-dependent transport processes.
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D008756:Methylgalactosides / Q000378:metabolism*; D008759:Methylglycosides / Q000378:metabolism*; D011392:Proline / Q000378:metabolism*; D013862:Thiogalactosides / Q000378:metabolism* / Q000494:pharmacology; D013865:Thioglycosides / Q000378:metabolism*
chemical_list: D008756:Methylgalactosides; D008759:Methylglycosides; D013862:Thiogalactosides; D013865:Thioglycosides; C009468:thiomethylgalactoside; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D011392:Proline