title: Na+ transport via Na+/H+ antiport in Halobacterium halobium envelope vesicles.
abstract: Using H. halobium cell envelope vesicles containing either bacteriorhodopsin plus Na+ pump, bacteriorhodopsin alone, Na+ pump alone, or no light-responsive pigment altogether, it could be shown that the large majority of light energized Na+ extrusion in these mutants is linked to bacteriorhodopsin and to protonmotive force, and therefore must be facilitated by a Na+/H+ antiporter. Thus, the recently discovered primary Na+ pump makes only a minor contribution to light-mediated Na+ flux. The activity of the Na+/H+ antiporter appears to be independent of the presence of any photoreactive pigments, since an artifical electron donor will drive rapid Na+ extrusion in all of the vesicle preparations tested.
mesh_terms: D001436:Bacteriorhodopsins / Q000378:metabolism*; D001692:Biological Transport; D001693:Biological Transport, Active; D002338:Carotenoids / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005971:Glutamates; D006217:Halobacterium / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers; D013053:Spectrophotometry
chemical_list: D002352:Carrier Proteins; D005971:Glutamates; D017923:Sodium-Hydrogen Exchangers; D002338:Carotenoids; D001436:Bacteriorhodopsins; D012964:Sodium