Most mammalian cells transport glucose through a family of membrane proteins known as glucose transporters. Molecular cloning of these glucose transporters has identified a family of closely related genes that encodes at least 7 proteins (GLUT 1 to GLUT 13, Mol. Wt. 40-80kD) and Sodium glucose co-transporter-1 (SGLT-1, 662aa; ~75kD). Individual members of this family have identical predicted secondary structures with 12 transmembrane domains. Both N- and C-termini are predicted to be cytoplasmic. Most differences in sequence homology exist within the four hydrophilic domains that may play a role in tissue-specific targeting. Glut isoforms differ in their tissue expression, substrate specificity and kinetic characteristics. GLUT 2 provides glucose to the liver and pancreatic cells.