Facilitative glucose transporter, which is responsible for constitutive or basal glucose uptake (  ). Has a very broad substrate specificity; can transport a wide range of aldoses including both pentoses and hexoses (, ). Most important energy carrier of the brain: present at the blood-brain barrier and assures the energy-independent, facilitative transport of glucose into the brain . In association with BSG and NXNL1, promotes retinal cone survival by increasing glucose uptake into photoreceptors (By similarity). Required for mesendoderm differentiation (By similarity).
Subcellular locations: Cell membrane, Melanosome, Photoreceptor inner segment
Localizes primarily at the cell surface (  ). Identified by mass spectrometry in melanosome fractions from stage I to stage IV .
Detected in erythrocytes (at protein level). Expressed at variable levels in many human tissues.