Expression Cloning and Characterization of a Novel Sodium-Dicarboxylate Cotransporter from Winter Flounder Kidney

• Published in: The Journal of biological chemistry 1999-07, Vol.274 (29), p.20191-20196
• Main Authors: Steffgen, Jürgen, Burckhardt, Birgitta C., Langenberg, Christoph, Kühne, Lars, Müller, Gerhard A., Burckhardt, Gerhard, Wolff, Natascha A.
• Format: Article
• Language: English
• Subjects: 2,3-dimethylsuccinate; aconitate; Amino Acid Sequence; Animals; Base Sequence; basolateral membranes; Carrier Proteins - chemistry; Carrier Proteins - genetics; Cloning, Molecular; Dicarboxylic Acid Transporters; DNA, Complementary; Flounder; Humans; Kidney - metabolism; Marine; Membrane Proteins - chemistry; Membrane Proteins - genetics; Molecular Sequence Data; Na super(+)/dicarboxylate cotransporter; Organic Anion Transporters, Sodium-Dependent; Protein Structure, Secondary; Pseudopleuronectes americanus; Sequence Homology, Amino Acid; sodium/dicarboxylate cotransporter; succinate; Symporters; Xenopus laevis
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.29.20191

A cDNA coding for a Na + -dicarboxylate cotransporter, fNaDC-3, from winter flounder ( Pseudopleuronectes americanus ) kidney was isolated by functional expression in Xenopus laevis oocytes. The fNaDC-3 cDNA is 2384 nucleotides long and encodes a protein of 601 amino acids with a calculated molecular mass of 66.4 kDa. Secondary structure analysis predicts at least eight membrane-spanning domains. Transport of succinate by fNaDC-3 was sodium-dependent, could be inhibited by lithium, and evoked an inward current. The apparent affinity constant ( K m ) of fNaDC-3 for succinate of 30 μ m resembles that of Na + -dicarboxylate transport in the basolateral membrane of mammalian renal proximal tubules. The substrates specific for the basolateral transporter, 2,3-dimethylsuccinate and cis -aconitate, not only inhibited succinate uptake but also evoked inward currents, proving that they are transported by fNaDC-3. Succinate transport via fNaDC-3 decreased by lowering pH, as did citrate transport, although much more moderately. These characteristics suggest that fNaDC-3 is a new type of Na + -dicarboxylate transporter that most likely corresponds to the Na + -dicarboxylate cotransporter in the basolateral membrane of mammalian renal proximal tubules.