Divalent anion–sodium symporter

Last updated
Identifiers
SymbolDASS
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.

Contents

Structure

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

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:

  1. all animal homologues;
  2. all yeast proteins;
  3. a functionally uncharacterized protein from Ralstonia eutrophus;
  4. three E. coli proteins plus one from H. influenzae and one from spinach chloroplasts (the SodiT1 oxoglutarate:malate translocator);
  5. an E. coli Orf that clusters loosely with a sulfur deprivation regulated protein of Synechocystis, and
  6. 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

Functionally characterized proteins of the DASS family (also called the SLC13 family) transport:

  1. organic di- and tricarboxylates of the Krebs Cycle as well as dicarboxylate amino acid,
  2. 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

Related Research Articles

Cotransporter

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The Transporter Classification Database is an International Union of Biochemistry and Molecular Biology (IUBMB)-approved classification system for membrane transport proteins, including ion channels.

The sodium/phosphate cotransporter is a member of the phosphate:Na+ symporter (PNaS) family within the TOG Superfamily of transport proteins as specified in the Transporter Classification Database (TCDB).

Mitochondrial carrier large group of transport proteins

Mitochondrial carriers are proteins from a solute carrier family which transfer molecules across the membranes of the mitochondria. Mitochondrial carriers are also classified in the Transporter Classification Database. The Mitochondrial Carrier (MC) Superfamily has been expanded to include both the original Mitochondrial Carrier (MC) family and the Mitochondrial Inner/Outer Membrane Fusion (MMF) family.

An amino acid transporter is a membrane transport protein that transports amino acids. They are mainly of the solute carrier family.

A carboxylate transporter is a membrane transport protein that transports carboxylate.

SLC13A3 protein-coding gene in the species Homo sapiens

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SLC13A2 protein-coding gene in the species Homo sapiens

Solute carrier family 13 member 2 is a protein that is encoded in humans by the SLC13A2 gene.

The Nucleobase:Cation Symporter-1 (NCS1) Family (TC# 2.A.39) consists of over 1000 currently sequenced proteins derived from Gram-negative and Gram-positive bacteria, archaea, fungi and plants. These proteins function as transporters for nucleobases including purines and pyrimidines. Members of this family possess twelve transmembrane α-helical spanners (TMSs). At least some of them have been shown to function in uptake by substrate:H+ symport mechanism.

Sodium-solute symporter group of transport proteins

Members of the Solute:Sodium Symporter (SSS) Family (TC# 2.A.21) catalyze solute:Na+ symport. The SSS family is within the APC Superfamily. The solutes transported may be sugars, amino acids, organo cations such as choline, nucleosides, inositols, vitamins, urea or anions, depending on the system. Members of the SSS family have been identified in bacteria, archaea and eukaryotes. Almost all functionally well-characterized members normally catalyze solute uptake via Na+ symport.

Organic anion transporter 1 protein-coding gene in the species Homo sapiens

The organic anion transporter 1 (OAT1) also known as solute carrier family 22 member 6 (SLC22A6) is a protein that in humans is encoded by the SLC22A6 gene. It is a member of the organic anion transporter (OAT) family of proteins. OAT1 is a transmembrane protein that is expressed in the brain, the placenta, the eyes, smooth muscles, and the basolateral membrane of proximal tubular cells of the kidneys. It plays a central role in renal organic anion transport. Along with OAT3, OAT1 mediates the uptake of a wide range of relatively small and hydrophilic organic anions from plasma into the cytoplasm of the proximal tubular cells of the kidneys. From there, these substrates are transported into the lumen of the nephrons of the kidneys for excretion. OAT1 homologs have been identified in rats, mice, rabbits, pigs, flounders, and nematodes.

Sodium sulfate symporters are integral membrane proteins that mediate the intake of a wide variety of molecules with the concomitant uptake of sodium ions. These sodium symporters can be grouped, on the basis of sequence and functional similarities into a number of distinct families. One of these families, also known as SLC13 transporters, consists of the following proteins:

SLC13A5 protein-coding gene in the species Homo sapiens

Solute carrier family 13 (sodium-dependent citrate transporter), member 5 also known as the Na+/citrate cotransporter or mIndy is a protein that in humans is encoded by the SLC13A5 gene. It is the mammalian homolog of the fly Indy (gene).

The amino acid-polyamine-organocation (APC) superfamily is the second largest superfamily of secondary carrier proteins currently known, and it contain several Solute carriers. Originally, the APC superfamily consisted of subfamilies under the transporter classification number 2.A.3. This superfamily has since been expanded to include eighteen different families.

The cation-chloride cotransporter (CCC) family is part of the APC superfamily of secondary carriers. Members of the CCC family are found in animals, plants, fungi and bacteria. Most characterized CCC family proteins are from higher eukaryotes, but one has been partially characterized from Nicotiana tabacum, and homologous ORFs have been sequenced from Caenorhabditis elegans (worm), Saccharomyces cerevisiae (yeast) and Synechococcus sp.. The latter proteins are of unknown function. These proteins show sequence similarity to members of the APC family. CCC family proteins are usually large, and possess 12 putative transmembrane spanners (TMSs) flanked by large N-terminal and C-terminal hydrophilic domains.

The anion exchanger family is a member of the large APC superfamily of secondary carriers. Members of the AE family are generally responsible for the transport of anions across cellular barriers, although their functions may vary. Characterized protein members of the AE family are found in plants, animals, insects and yeast. Uncharacterized AE homologues may be present in bacteria. Animal AE proteins consist of homodimeric complexes of integral membrane proteins that vary in size from about 900 amino acyl residues to about 1250 residues. Their N-terminal hydrophilic domains may interact with cytoskeletal proteins and therefore play a cell structural role. Some of the currently characterized members of the AE family can be found in the Transporter Classification Database.

The sulfate permease (SulP) family is a member of the large APC superfamily of secondary carriers. The SulP family is a large and ubiquitous family of proteins derived from archaea, bacteria, fungi, plants and animals. Many organisms including Bacillus subtilis, Synechocystis sp, Saccharomyces cerevisiae, Arabidopsis thaliana and Caenorhabditis elegans possess multiple SulP family paralogues. Many of these proteins are functionally characterized, and most are inorganic anion uptake transporters or anion:anion exchange transporters. Some transport their substrate(s) with high affinities, while others transport it or them with relatively low affinities. Others may catalyze SO2−
4:HCO−
3 exchange, or more generally, anion:anion antiport. For example, the mouse homologue, SLC26A6, can transport sulfate, formate, oxalate, chloride and bicarbonate, exchanging any one of these anions for another. A cyanobacterial homologue can transport nitrate. Some members can function as channels. SLC26A3 and SLC26A6 can function as carriers or channels, depending on the transported anion. In these porters, mutating a glutamate, also involved in transport in the CIC family, created a channel out of the carrier. It also changed the stoichiometry from 2Cl−/HCO−
3 to 1Cl−/HCO−
3.

The ion transporter (IT) superfamily is a superfamily of secondary carriers that transport charged substrates.

The Malonate Uptake (MatC) family is a constituent of the ion transporter (IT) superfamily. It consists of proteins from Gram-negative and Gram-positive bacteria, simple eukaryotes and archaea. The proteins are of about 450 amino acyl residues in length with 12-14 putative transmembrane segments (TMSs). Closest functionally-characterized homologues are in the DASS family. One member of this family is a putative malonate transporter.

The inorganic phosphate transporter (PiT) family is a group of carrier proteins derived from Gram-negative and Gram-positive bacteria, archaea, and eukaryotes.

References

  1. 1 2 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.
  2. ↑ 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.
  3. 1 2 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.
  4. ↑ 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.
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