{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"GLUT proteins are members of the major facilitator superfamily of membrane transporters. The 14 GLUT proteins are categorized into 3 classes based on sequence similarity. GLUT1 primarily transports glucose, but is also capable of transporting mannose, galactose, glucosamine, and dehydroascorbic acid. GLUT1 is a type III integral protein with 12 transmembrane helices and an N-linked glycosylation site at N45. It is expressed at its highest level in erythrocytes. GLUT1 expression is also found in the brain astrocytes, blood-brain barrier, blood-tissue barrier, placenta, and fetal tissues. Tumors are highly dependent on the generation of ATP via aerobic glycolysis, thus explaining the necessity for the increased expression of GLUT1, which has been linked to tumor progression or poor survival of patients."}]}]}