The GLUT protein family is a member of the major facilitator superfamily of membrane transporters and is encoded by the SLC2 genes. GLUT proteins contain 12 membrane-spanning domains, an N-linked glycosylation site, and intracellular NH2 and COOH termini. In addition there are several conserved residues and motifs designated “sugar transporter signatures”.
To date, 14 GLUT isoforms have been identified and divided into 3 different classes based on sequence similarity and structural and functional characteristics. GLUT4 together with GLUT 1-3 and 14 belong to Class I.