Divalent anion–sodium symporter
| Identifiers | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Symbol | DASS | ||||||||
| Pfam | PF00939 | ||||||||
| TCDB | 2.A.47 | ||||||||
| OPM superfamily | 272 | ||||||||
| OPM protein | 4f35 | ||||||||
| |||||||||
Divalent anion:Na+ symporters were found in bacteria, archaea, plant chloroplasts and animals.
Structure
[edit]They vary in size from 432 amino acyl residues (M. jannaschii) to 923 residues (Saccharomyces cerevisiae). The three S. cerevisiae proteins are large (881-923 residues); the animal proteins are substantially smaller (539-616 residues), and the bacterial proteins are still smaller (461-612 residues). They exhibit 11-14 putative transmembrane α-helical spanners (TMSs). An 11 TMS model for the animal NaDC-1 and hNaSi-1 carriers has been proposed.[1][2] Two serine residues in the human sulfate transporter, hNaSi-1 (TC# 2.A.47.1.16; Q9BZW2), one in TMS 5 and one in TMS 6, are required for sulfate transport.[1] The former carrier and the other NaDC isoforms cotransport 3 Na+ with each dicarboxylate. Protonated tricarboxylates are also cotransported with 3 Na+. Several organisms possess multiple paralogues of the DASS family (e.g., 4 for E. coli; 2 for H. influenzae, 3 for S. cerevisiae, and at least 4 for C. elegans).
Homology
[edit]Proteins of the DASS family are divided into two groups of transporters with distinct anion specificities: the Na+-sulfate (NaS) cotransporters and the Na+-carboxylate (NaC) cotransporters. Mammalian members of this family are: SLC13A1 (NaS1), SLC13A2 (NaC1), SLC13A3 (NaC3), SLC13A4 (NaS2) and SLC13A5 (NaC2).[3] DASS family proteins encode plasma membrane polypeptides with 8-13 putative transmembrane domains, and are expressed in a variety of tissues. They are all Na+-coupled symporters. The Na+:anion coupling ratio is 3:1, indicative of electrogenic properties. They have a substrate preference for divalent anions, which include tetra-oxyanions for the NaS cotransporters or Krebs cycle intermediates (including mono-, di- and tricarboxylates) for the NaC cotransporters. The molecular and cellular mechanisms underlying the biochemical, physiological and structural properties of DASS family members have been reviewed.[3]
The phylogenetic tree for the DASS family reveals six clusters as follows:
- all animal homologues;
- all yeast proteins;
- a functionally uncharacterized protein from Ralstonia eutrophus;
- three E. coli proteins plus one from H. influenzae and one from spinach chloroplasts (the SodiT1 oxoglutarate:malate translocator);
- an E. coli Orf that clusters loosely with a sulfur deprivation regulated protein of Synechocystis, and
- an M. jannaschii protein that clusters loosely with an H. influenzae Orf.
Distant homologues of DASS family proteins may include members of the Ars (arsenite exporter) (TC# 3.A.4) family as well as the NhaB (TC #2.A.34) and NhaC (TC #2.A.35) Na+/H+ antiporter families. The DASS family is therefore a member of the ion transporter (IT) superfamily.[4]
Function
[edit]Functionally characterized proteins of the DASS family (also called the SLC13 family) transport:
- organic di- and tricarboxylates of the Krebs Cycle as well as dicarboxylate amino acid,
- inorganic sulfate and (3) phosphate.
The generalized transport reaction catalyzed by the DASS family proteins is probably:
Anion2− (out) + nM+ [Na+ or H+] (out) → Anion2− (in) + nM+ (in).
See also
[edit]- Solute carrier family
- Ion transporters
- Transport protein
- Membrane transport protein
- Transporter Classification Database
References
[edit]- ^ a b Li H, Pajor AM (September 2003). "Serines 260 and 288 are involved in sulfate transport by hNaSi-1". The Journal of Biological Chemistry. 278 (39): 37204–12. doi:10.1074/jbc.M305465200. PMID 12857732.
- ^ Pajor AM (1999-01-01). "Sodium-coupled transporters for Krebs cycle intermediates". Annual Review of Physiology. 61: 663–82. doi:10.1146/annurev.physiol.61.1.663. PMID 10099705.
- ^ a b Markovich D (2012-01-01). "Sodium-sulfate/carboxylate cotransporters (SLC13)". Current Topics in Membranes. 70: 239–56. doi:10.1016/B978-0-12-394316-3.00007-7. ISBN 9780123943163. PMID 23177988.
- ^ Rabus R, Jack DL, Kelly DJ, Saier MH (December 1999). "TRAP transporters: an ancient family of extracytoplasmic solute-receptor-dependent secondary active transporters". Microbiology. 145 ( Pt 12) (12): 3431–45. doi:10.1099/00221287-145-12-3431. PMID 10627041.
