title: Functionally important amino acids in rice sucrose transporter OsSUT1.
abstract: Six conserved, charged amino acids within membrane spans in rice sucrose transporter OsSUT1 were identified using a three-dimensional structural model based on the crystal structures of three major facilitator superfamily (MFS) proteins: LacY, GlpT, and EmrD. These positions in OsSUT1 were selected for mutagenesis and biochemical assays. Among the six mutants, D177N completely lost transport function, D331N retained only a small fraction of sucrose uptake activity (2.3% of that of the wild type), and R335H and E336Q also displayed a substantial decrease in transport activity. D329N functioned as well as wild-type OsSUT1. R188K did not transport sucrose but showed a H(+) leak that was inhibited by sucrose, indicating that R188K had uncoupled sucrose and H(+) translocation. This demonstrates that charged amino acids within membrane spans are important for the transport mechanism of OsSUT1 as they are in lactose permease.
authors.affiliation: Department of Plant Biology, University of Minnesota-Twin Cities, St. Paul, Minnesota 55108, United States.
authors.forename: Ye
authors.initials: Y
authors.lastname: Sun
authors.forename: Zi
authors.initials: Z
authors.lastname: Lin
authors.forename: Anke
authors.initials: A
authors.lastname: Reinders
authors.forename: John M
authors.initials: JM
authors.lastname: Ward
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry*; D000818:Animals; D001692:Biological Transport; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012275:Oryza / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D013395:Sucrose / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D000596:Amino Acids; D026901:Membrane Transport Proteins; D010940:Plant Proteins; C078729:sucrose transport protein, plant; D013395:Sucrose; C021499:lactose permease