Stimulation of 32Pi transport into human erythrocyte ghosts and reconstituted vesicles by Mg2+ and hemoglobin

Human erythrocyte ghosts catalyze a low rate of 32Pi uptake. A severalfold stimulation of 32Pi uptake was observed after exposure of the membranes to an erythrocyte lysate or to hemoglobin in the presence of Mg2+. Ghosts prepared from erythrocytes that had been exposed to 10 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid showed a marked reduction in 32Pi uptake. Reconstitution of membranes with added phospholipids by freezing and thawing, by octylglucoside dilution or by cholate dialysis, yielded vesicles that catalyzed 32Pi uptake. When membranes were incubated with hemoglobin and Mg2+ prior to reconstitution, the rate of uptake was increased severalfold. The inhibition of hemoglobin and Mg2+-dependent uptake of 32Pi by chloride suggests that the transport in the reconstituted vesicles is catalyzed by the classical inorganic anion transporter.