title: Transport and signaling via the amino acid binding site of the yeast Gap1 amino acid transceptor.
abstract: Transporter-related nutrient sensors, called transceptors, mediate nutrient activation of signaling pathways through the plasma membrane. The mechanism of action of transporting and nontransporting transceptors is unknown. We have screened 319 amino acid analogs to identify compounds that act on Gap1, a transporting amino acid transceptor in yeast that triggers activation of the protein kinase A pathway. We identified competitive and noncompetitive inhibitors of transport, either with or without agonist action for signaling, including nontransported agonists. Using substituted cysteine accessibility method (SCAM) analysis, we identified Ser388 and Val389 as being exposed into the amino acid binding site, and we show that agonist action for signaling uses the same binding site as used for transport. Our results provide the first insight, to our knowledge, into the mechanism of action of transceptors. They indicate that signaling requires a ligand-induced specific conformational change that may be part of but does not require the complete transport cycle.
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Katholieke Universiteit Leuven, Kasteelpark Arenberg 31, B-3001 Leuven-Heverlee, Flanders, Belgium.
authors.forename: Griet
authors.initials: G
authors.lastname: Van Zeebroeck
authors.forename: Beatriz Monge
authors.initials: BM
authors.lastname: Bonini
authors.forename: Matthias
authors.initials: M
authors.lastname: Versele
authors.forename: Johan M
authors.initials: JM
authors.lastname: Thevelein
mesh_terms: D026905:Amino Acid Transport Systems / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D020134:Catalytic Domain; D004151:Dipeptides / Q000494:pharmacology; D015966:Gene Expression Regulation, Fungal / Q000502:physiology; D016296:Mutagenesis; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D026905:Amino Acid Transport Systems; D000596:Amino Acids; D004151:Dipeptides; C491145:GAP1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins