Solubilization and functional reconstitution of the DCCD-sensitive Na+/H(+)-antiporter from Halobacterium halobium

Na+/H+ exchange activity was solubilized from Halobacterium halobium with octyl-beta-D-glucoside (OG) and was reconstituted into the bacterio-rhodopsin incorporated liposomes (BR-liposomes) by the detergent-dialysis method. Light illumination stimulated uphill 22Na+ uptake into the reconstituted conjugate proteoliposomes. The 22Na+ uptake was FCCP-sensitive and was dependent on the amounts of OG-extract applied. On the other hand, the proteoliposomes reconstituted with the membrane fraction pretreated with N,N'-dicyclohexylcarbodiimide (DCCD) did not exhibit the light-dependent 22Na+ uptake, thus, DCCD-sensitive. When the reconstituted proteoliposome was incubated with 14C]DCCD, radio-labels appeared slightly on 50K but mainly on 11K-Dalton component, which are the same components labeled in the intact membrane vesicles. It is concluded that halobacterial DCCD-sensitive Na+/H(+)-antiporter was solubilized and reconstituted in the conjugate BR-liposomes with preserved functional unit.