Active transport of biogenic amines in chromaffin granule membrane vesicles

Chromaffin granule membrane vesicles accumulate large amounts of catecholamines against their concentration gradients. This process is ATP-dependent, reserpine, FCCP and nigericin sensitive. Carrier-mediated, reserpine-sensitive accumulation has also been demonstrated in the absence of ATP when a pH gradient (delta pH) is artificially generated across the membrane. Crude preparation of 5-hydroxytryptamine storage vesicles from rat brain or from pig platelets showed similar requirement of a transmembrane pH gradient for accumulation of the amine. The catecholamine transporter from chromaffin granules has been solubilized by the use of detergents in the presence of phospholipids. Removal of the detergent either by Sephadex filtration or by dialysis results in the formation of proteoliposomes which catalyze delta pH-dependent, reserpine-sensitive catecholamine accumulation. Under proper conditions, the solubilized H+-translocating ATPase has been incorporated into the same proteoliposomes with the catecholamine transporter, and ATP-dependent transport has been measured. The reconstituted protein shows specificity and affinity towards catecholamines similar to the native one.