Class 2 Glucose transporters (GLUTs) of the Major Facilitator Superfamily
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). GLUT5, also called Solute carrier family 2, facilitated glucose transporter member 5 (SLC2A5), is a well-established fructose transporter found in the small intestine. GLUT7 (or SLC2A7) is a high-affinity glucose and fructose transporter expressed in the small intestine and colon. GLUT9 (or SLC2A9) transports urate and fructose, and is most strongly expressed in the basolateral membranes of proximal renal tubular cells, liver and placenta. It may play a role in urate reabsorption by proximal tubules. GLUT11 (or SLC2A11) is a facilitative glucose transporter expressed in heart and skeletal muscle. 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.
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