DCCD-sensitive Na+-transport in the membrane vesicles of Halobacterium halobium.
The effects of N,N'-dicyclohexylcarbodiimide (DCCD) and various ionophores on light-induced 22Na+-transport were studied in right-side-out membrane vesicles from Halobacterium halobium R1M1. The light-induced Na+ efflux was inhibited at the same DCCD concentration (greater than 40 nmol/mg protein) as required for inhibition of the Na+-dependent membrane potential (delta phi) formation. This supports our previous indication that the DCCD-sensitive, Na+-dependent transformation of pH-gradient (delta pH) into delta phi is mediated by Na+/H+-antiporter (Murakami, N. and Konishi, T. (1985) J. Biochem. 98, 897-907). FCCP or a combination of valinomycin and triphenyltin (TPT) inhibits the light-induced Na+ efflux in accordance with the notion of protonmotive force (delta mu H+)-driven antiporter. However, a marked lag in initiation of the Na+ efflux occurred in the presence of valinomycin, TPMP+, or a small amount of FCCP, suggesting that a gating step is involved in the Na+ efflux. On the other hand, the delta pH-dissipating ionophore TPT did not cause the lag. A simultaneous determination of delta phi, delta pH, and Na+ efflux rate at the initial stage of illumination revealed that the antiporter is gated by delta phi rather than delta mu H+.
Murakami
N
N
Department of Radiochemistry-Biology, Niigata College of Pharmacy.
Konishi
T
T
D001692:Biological Transport; D002234:Carbodiimides / Q000494:pharmacology*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology*; D006217:Halobacterium / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D006863:Hydrogen-Ion Concentration; D008027:Light; D009861:Onium Compounds / Q000494:pharmacology; D009947:Organotin Compounds / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D014320:Triphenylmethyl Compounds / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology
D002234:Carbodiimides; D009861:Onium Compounds; D009947:Organotin Compounds; D014320:Triphenylmethyl Compounds; C011561:triphenylmethylphosphonium; D014634:Valinomycin; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D004024:Dicyclohexylcarbodiimide; D012964:Sodium; C012594:triphenyltin chloride