Glucose transporter (GLUT) types 6 and 8, Class 3 GLUTs, and similar transporters of the Major Facilitator Superfamily
This subfamily is composed of glucose transporter type 6 (GLUT6), GLUT8, plant early dehydration-induced gene ERD6-like proteins, and similar insect proteins including facilitated trehalose transporter Tret1-1. GLUTs, also called Solute carrier family 2, facilitated glucose transporters (SLC2A), are a family of proteins that facilitate the transport of hexoses such as glucose and fructose. There are fourteen GLUTs found in humans; they display different substrate specificities and tissue expression. They have been categorized into three classes based on sequence similarity: Class 1 (GLUTs 1-4, 14); Class 2 (GLUTs 5, 7, 9, and 11); and Class 3 (GLUTs 6, 8, 10, 12, and HMIT). Insect Tret1-1 is a low-capacity facilitative transporter for trehalose that mediates the transport of trehalose synthesized in the fat body and the incorporation of trehalose into other tissues that require a carbon source. GLUT proteins are comprised of about 500 amino acid residues, possess a single N-linked oligosaccharide, and have 12 transmembrane segments. They belong to the Glucose transporter -like (GLUT-like) family of the Major Facilitator Superfamily (MFS) of membrane transport proteins. MFS proteins are thought to function through a single substrate binding site, alternating-access mechanism involving a rocker-switch type of movement.