title: Sequence determinants of GLUT1-mediated accelerated-exchange transport: analysis by homology-scanning mutagenesis.
abstract: The class 1 equilibrative glucose transporters GLUT1 and GLUT4 are structurally similar but catalyze distinct modes of transport. GLUT1 exhibits trans-acceleration, in which the presence of intracellular sugar stimulates the rate of unidirectional sugar uptake. GLUT4-mediated uptake is unaffected by intracellular sugar. Using homology-scanning mutagenesis in which domains of GLUT1 are substituted with equivalent domains from GLUT4 and vice versa, we show that GLUT1 transmembrane domain 6 is both necessary and sufficient for trans-acceleration. This region is not directly involved in GLUT1 binding of substrate or inhibitors. Rather, transmembrane domain 6 is part of two putative scaffold domains, which coordinate membrane-spanning amphipathic helices that form the sugar translocation pore. We propose that GLUT1 transmembrane domain 6 restrains import when intracellular sugar is absent by slowing transport-associated conformational changes.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
authors.forename: Sabrina S
authors.initials: SS
authors.lastname: Vollers
authors.forename: Anthony
authors.initials: A
authors.lastname: Carruthers
mesh_terms: D000595:Amino Acid Sequence; D055162:Biocatalysis; D001692:Biological Transport; D050260:Carbohydrate Metabolism; D002462:Cell Membrane / Q000378:metabolism; D003847:Deoxyglucose / Q000378:metabolism; D051272:Glucose Transporter Type 1 / Q000737:chemistry* / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000737:chemistry / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000235:genetics*; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
chemical_list: D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D050505:Mutant Proteins; D003847:Deoxyglucose