title: Determinants of substrate and cation transport in the human Na+/dicarboxylate cotransporter NaDC3.
abstract: Metabolic intermediates, such as succinate and citrate, regulate important processes ranging from energy metabolism to fatty acid synthesis. Cytosolic concentrations of these metabolites are controlled, in part, by members of the SLC13 gene family. The molecular mechanism underlying Na(+)-coupled di- and tricarboxylate transport by this family is understood poorly. The human Na(+)/dicarboxylate cotransporter NaDC3 (SLC13A3) is found in various tissues, including the kidney, liver, and brain. In addition to citric acid cycle intermediates such as α-ketoglutarate and succinate, NaDC3 transports other compounds into cells, including N-acetyl aspartate, mercaptosuccinate, and glutathione, in keeping with its dual roles in cell nutrition and detoxification. In this study, we construct a homology structural model of NaDC3 on the basis of the structure of the Vibrio cholerae homolog vcINDY. Our computations are followed by experimental testing of the predicted NaDC3 structure and mode of interaction with various substrates. The results of this study show that the substrate and cation binding domains of NaDC3 are composed of residues in the opposing hairpin loops and unwound portions of adjacent helices. Furthermore, these results provide a possible explanation for the differential substrate specificity among dicarboxylate transporters that underpin their diverse biological roles in metabolism and detoxification. The structural model of NaDC3 provides a framework for understanding substrate selectivity and the Na(+)-coupled anion transport mechanism by the human SLC13 family and other key solute carrier transporters.
authors.affiliation: From the Department of Pharmacology and Systems Therapeutics, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York 10029 and avner.schlessinger@mssm.edu.
authors.forename: Avner
authors.initials: A
authors.lastname: Schlessinger
authors.affiliation: the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92130-0718.
authors.forename: Nina N
authors.initials: NN
authors.lastname: Sun
authors.affiliation: From the Department of Pharmacology and Systems Therapeutics, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York 10029 and.
authors.forename: Claire
authors.initials: C
authors.lastname: Colas
authors.affiliation: the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92130-0718 apajor@ucsd.edu.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Pajor
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D019556:COS Cells; D002522:Chlorocebus aethiops; D019343:Citric Acid / Q000378:metabolism; D006801:Humans; D017136:Ion Transport; D008094:Lithium / Q000378:metabolism; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D029363:Organic Anion Transporters, Sodium-Dependent / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D016415:Sequence Alignment; D012964:Sodium / Q000378:metabolism*; D013379:Substrate Specificity; D019802:Succinic Acid / Q000378:metabolism; D027981:Symporters / Q000737:chemistry* / Q000378:metabolism; D014734:Vibrio cholerae / Q000737:chemistry / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029363:Organic Anion Transporters, Sodium-Dependent; C568530:SLC13A3 protein, human; D027981:Symporters; D019343:Citric Acid; D008094:Lithium; D012964:Sodium; D019802:Succinic Acid
keywords: Citrate; Homology Modeling; Membrane; Molecular Docking; SLC13 Family; Sodium Transport; Succinate; Tricarboxylic Acid Cycle (TCA Cycle) (Krebs Cycle)