title: Two regions of GLUT 2 glucose transporter protein are responsible for its distinctive affinity for glucose.
abstract: The glucose transporter in the hepatocyte and pancreatic beta-cell (GLUT 2) has a lower affinity for glucose than other members of the glucose transporter family. To investigate the molecular mechanism for the distinctive affinity of GLUT 2 for glucose, we expressed chimeric GLUT 2 and GLUT 4 proteins in Xenopus oocytes and measured 3-O-methyl-D-glucose transport. In the oocyte system, GLUT 2 had a Km of 31.8 +/- 2.8 mM for 3-O-methyl-D-glucose, whereas GLUT 4 had a Km of 7.2 +/- 2.4 mM under equilibrium exchange conditions. GLUT 4/GLUT 2 chimera that contained the intracellular loop and transmembrane domains 7-12 of GLUT 2 (amino acids 239-497) had a Km similar to that of wild-type GLUT 2. A GLUT 4/GLUT 2 chimera in which the COOH-terminal 30 amino acids of GLUT 4 were replaced with the corresponding region of GLUT 2 had a 2-fold higher Km than GLUT 4, but still had a much lower Km than GLUT 2. These results indicate that both transmembrane domains 7-12 and the COOH-terminus of the protein are responsible for the distinctive glucose affinity of GLUT 2.
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
authors.forename: A
authors.initials: A
authors.lastname: Buchs
authors.forename: L
authors.initials: L
authors.lastname: Wu
authors.forename: H
authors.initials: H
authors.lastname: Morita
authors.forename: R R
authors.initials: RR
authors.lastname: Whitesell
authors.forename: A C
authors.initials: AC
authors.lastname: Powers
mesh_terms: D000818:Animals; D005260:Female; D005947:Glucose / Q000378:metabolism*; D051273:Glucose Transporter Type 2; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D009124:Muscle Proteins; D009865:Oocytes / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014982:Xenopus laevis
chemical_list: D051273:Glucose Transporter Type 2; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D011993:Recombinant Fusion Proteins; D005947:Glucose