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This Article Full Text Full Text (PDF) All Versions of this Article: 289/5/C1159    most recent 00295.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Oshiro, N. Articles by Pajor, A. M. Search for Related Content PubMed PubMed Citation Articles by Oshiro, N. Articles by Pajor, A. M.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Functional characterization of high-affinity Na⁺/dicarboxylate cotransporter found in Xenopus laevis kidney and heart

Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, Texas

Submitted 23 June 2004 ; accepted in final form 5 June 2005

The SLC13 gene family includes sodium-coupled transporters for citric acid cycle intermediates and sulfate. The present study describes the sequence and functional characterization of a SLC13 family member from Xenopus laevis, the high-affinity Na⁺/dicarboxylate cotransporter xNaDC-3. The cDNA sequence of xNaDC-3 codes for a protein of 602 amino acids that is 70% identical to the sequences of mammalian NaDC-3 orthologs. The message for xNaDC-3 is found in the kidney, liver, intestine, and heart. The xNaDC-3 has a high affinity for substrate, including a K_m for succinate of 4 µM, and it is inhibited by the NaDC-3 test substrates 2,3-dimethylsuccinate and adipate. The transport of succinate by xNaDC-3 is dependent on sodium, with sigmoidal activation kinetics, and lithium can partially substitute for sodium. As with other members of the family, xNaDC-3 is electrogenic and exhibits inward substrate-dependent currents in the presence of sodium. However, other electrophysiological properties of xNaDC-3 are unique and involve large leak currents, possibly mediated by anions, that are activated by binding of sodium or lithium to a single site.

SLC13 gene family; citric acid cycle intermediate; lithium

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