Protein-mediated chloride-phosphate and lactate-lactate exchange in cytoskeleton-free vesicles budded from rabbit...

Spectrin-free budded vesicles from rabbit erythrocytes (Leonards, K.S. and Ohki, S. (1983) Biochim. Biophys. Acta 728, 383-393) exchange intravesicular L-[14C]lactate for extravesicular L-lactate and intravesicular [36C]chloride for extravesicular phosphate with inhibitor sensitivity consistent with what is seen in intact cells. The time-course of these fluxes is faster than for intact cells, but is somewhat slower than predicted from surface to volume ratios. Labelling with tritiated 4,4'-diisothiocyanyl-2,2'-dihydrostilbenedisulfonate (H2DIDS) at concentrations which selectively inhibit inorganic anion exchange or specific lactate exchange supports the involvement of a 93-110 kDa (band 3) polypeptide in anion transport and a 40-50 kDa polypeptide in lactate transport across these vesicle membranes. Since the budded vesicles have a markedly simplified protein profile on electrophoresis, their isolated membranes represent a preliminary stage in the purification of these transport proteins in which structure and function appear to be preserved.