Reconstitution of D-glucose transporter from human placental microvillous plasma membranes

Proteins from microvillous plasma membrane vesicles of the maternal surface of human trophoblast were solubilized with octyl beta-D-glucoside. After incorporation of the soluble protein into phospholipid liposomes D-glucose uptake exceeded that of L-glucose. The reconstituted system showed that D-glucose uptake was not sodium dependent and was inhibited by cytochalasin B. Efflux of D-glucose from the proteoliposomes was retarded by cytochalasin B. D-Glucose uptake, but not L-glucose, was proportional to the amount of protein used in the reconstitution procedure. Membrane protein was also solubilized with octylglucoside from vesicles that had been extracted previously by dimethylmaleic anhydride. Proteoliposomes prepared from these latter proteins showed D-glucose uptake threefold greater than that from octylglucoside solubilization alone, but sodium dodecyl sulfate polyacrylamide gel electrophoresis of the extracted protein showed no clear difference between the double extraction procedure and the pattern obtained with the single detergent.