Glucose transporters in chromaffin cells: Subcellular distribution and characterization

The glucose transporter was identified and characterized by cytochalasin B binding in subcellular membrane fractions of chromaffin tissue. The binding was saturable with a K d of about 0.3 μM for each subcellular fraction. The B max capacity was 12–16 pmol/mg protein for enriched plasma membrane fractions, 6.3 pmol/mg protein for microsomal membrane preparations and 5.4 pmol/mg protein for chromaffin granule membranes. Irreversible photoaffinity labelling of the glucose-protectable binding sites with [ 3H]cytochalasin B followed by solubilization and polyacrylamide gel electrophoresis from enriched plasma membrane preparations demonstrated the presence of three molecular species: 97±10, 51.5±6 and 30±4 kDa. The chromaffin granule membranes showed only a molecular species of 80±10 kDa.