title: Allosteric regulation of transport activity by heterotrimerization of Arabidopsis ammonium transporter complexes in vivo.
abstract: Ammonium acquisition by plant roots is mediated by AMMONIUM TRANSPORTERs (AMTs), ubiquitous membrane proteins with essential roles in nitrogen nutrition in all organisms. In microbial and plant cells, ammonium transport activity is controlled by ammonium-triggered feedback inhibition to prevent cellular ammonium toxicity. Data from heterologous expression in yeast indicate that oligomerization of plant AMTs is critical for allosteric regulation of transport activity, in which the conserved cytosolic C terminus functions as a trans-activator. Employing the coexpressed transporters AMT1;1 and AMT1;3 from Arabidopsis thaliana as a model, we show here that these two isoforms form functional homo- and heterotrimers in yeast and plant roots and that AMT1;3 carrying a phosphomimic residue in its C terminus regulates both homo- and heterotrimers in a dominant-negative fashion in vivo. (15)NH4(+) influx studies further indicate that allosteric inhibition represses ammonium transport activity in roots of transgenic Arabidopsis expressing a phosphomimic mutant together with functional AMT1;3 or AMT1;1. Our study demonstrates in planta a regulatory role in transport activity of heterooligomerization of transporter isoforms, which may enhance their versatility for signal exchange in response to environmental triggers.
authors: Department of Plant Nutrition, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
authors: Lixing
authors: L
authors: Yuan
authors: Riliang
authors: R
authors: Gu
authors: Yuanhu
authors: Y
authors: Xuan
authors: Erika
authors: E
authors: Smith-Valle
authors: Dominique
authors: D
authors: Loqué
authors: Wolf B
authors: WB
authors: Frommer
authors: Nicolaus
authors: N
authors: von Wirén
mesh_terms: D000494:Allosteric Regulation; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000494:pharmacology; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization; D021381:Protein Transport
chemical_list: D027682:Cation Transport Proteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D009566:Nitrates; D010940:Plant Proteins; D020033:Protein Isoforms; C088952:ammonium transporters, plant; C006568:ammonium nitrate