Summary: Sodium:solute symporter family
Pfam includes annotations and additional family information from a range of different sources. These sources can be accessed via the tabs below.
This is the Wikipedia entry entitled "Sodium-solute symporter". More...
The Wikipedia text that you see displayed here is a download from Wikipedia. This means that the information we display is a copy of the information from the Wikipedia database. The button next to the article title ("Edit Wikipedia article") takes you to the edit page for the article directly within Wikipedia. You should be aware you are not editing our local copy of this information. Any changes that you make to the Wikipedia article will not be displayed here until we next download the article from Wikipedia. We currently download new content on a nightly basis.
Does Pfam agree with the content of the Wikipedia entry ?
Pfam has chosen to link families to Wikipedia articles. In some case we have created or edited these articles but in many other cases we have not made any direct contribution to the content of the article. The Wikipedia community does monitor edits to try to ensure that (a) the quality of article annotation increases, and (b) vandalism is very quickly dealt with. However, we would like to emphasise that Pfam does not curate the Wikipedia entries and we cannot guarantee the accuracy of the information on the Wikipedia page.
Editing Wikipedia articles
Before you edit for the first time
Wikipedia is a free, online encyclopedia. Although anyone can edit or contribute to an article, Wikipedia has some strong editing guidelines and policies, which promote the Wikipedia standard of style and etiquette. Your edits and contributions are more likely to be accepted (and remain) if they are in accordance with this policy.
You should take a few minutes to view the following pages:
How your contribution will be recorded
Anyone can edit a Wikipedia entry. You can do this either as a new user or you can register with Wikipedia and log on. When you click on the "Edit Wikipedia article" button, your browser will direct you to the edit page for this entry in Wikipedia. If you are a registered user and currently logged in, your changes will be recorded under your Wikipedia user name. However, if you are not a registered user or are not logged on, your changes will be logged under your computer's IP address. This has two main implications. Firstly, as a registered Wikipedia user your edits are more likely seen as valuable contribution (although all edits are open to community scrutiny regardless). Secondly, if you edit under an IP address you may be sharing this IP address with other users. If your IP address has previously been blocked (due to being flagged as a source of 'vandalism') your edits will also be blocked. You can find more information on this and creating a user account at Wikipedia.
If you have problems editing a particular page, contact us at firstname.lastname@example.org and we will try to help.
The community annotation is a new facility of the Pfam web site. If you have problems editing or experience problems with these pages please contact us.
Sodium-solute symporter Edit Wikipedia article
|Sodium:solute symporter family|
Structure of Sodium/Sugar symporter with bound Galactose from vibrio parahaemolyticus.
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.
Sodium/substrate symport (or co-transport) is a widespread mechanism of solute transport across cytoplasmic membranes of pro- and eukaryotic cells. The energy stored in an inwardly directed electrochemical sodium gradient (sodium motive force, SMF) which is used to drive solute accumulation against a concentration gradient. The SMF is generated by primary sodium pumps (e.g. sodium/potassium ATPases, sodium translocating respiratory chain complexes) or via the action of sodium/proton antiporters. Sodium/substrate transporters are grouped in different families based on sequence similarities.
The human placental multivitamin symporter co-transports an anionic vitamin with two Na+. In the rabbit Na+:D-glucose co-transporter, SGLT1, the glucose translocation pathway probably involves TMSs 10-13, and the binding site for the inhibitor, phlorizin, involves loop 13 (residues 604-610). Cation binding in the N-terminal domain may induce transport-related conformational changes. A conserved tyrosine in the first transmembrane segment of solute:sodium symporters is involved in Na+-coupled substrate co-transport. Mechanistic aspects of Na+ binding sites in LeuT-like fold symporters has been discussed in detail.
Substrate Affinity in Humans
In the human homologue (hSGLT1), H+ can replace Na+, but the apparent affinity for glucose reduces 20x from 0.3 mM to 6 mM. The apparent affinity for H+ is 6 μM, 1000x higher than for Na+ (6 mM). The transport stoichiometry is 1 glucose to 2 Na+ or H+. If Asp204 is replaced by glutamate (D204E), the apparent affinity for H+ increases >20x with no change in apparent Na+ affinity. The D204N or D204C mutation promotes phlorizin-sensitive H+ currents that are 10x greater than Na+ currents, and the glucose:H+ stoichiometry is then as great as 1:145. The mutant system thus behaves as a glucose-gated H+ channel.
Proteins of the SSS vary in size from about 400 residues to about 700 residues and probably possess thirteen to fifteen putative transmembrane helical spanners (TMSs). They generally share a core of 13 TMSs, but different members of the family have different numbers of TMSs. A 13 TMS topology with a periplasmic N-terminus and a cytoplasmic C-terminus has been experimentally determined for the proline:Na+ symporter, PutP, of E. coli. Residues important for substrate and Na+ binding in PutP are found in TMSs 2, 7 and 9 as well as in adjacent loops. A 14 TMS topology with periplasmic N- and C-termini has been established for the Vibrio parahaemolyticus SglT carrier. SglT transports sugar:Na with a 1:1 stoichiometry. However, MctP of Rhizobium leguminosarum may take up monocarboxylates via an H+ symport mechanism as a dependency on Na+ could not be demonstrated and uptake was strongly inhibited by 10 μM CCP.
Faham et al., (2008) reported the crystal structure of a member of the solute:soduium symporter (SSS) family, the Vibrio parahaemolyticus sodium:galactose symporter, vSGLT (TC# 2.A.22.4.2) from the NSS family. Modeling the outward-facing conformation based on the LeuT structure, in conjunction with biophysical data, provided insight into structural rearrangements for active transport., ). The approximately 3.0 angstrom structure contains 14 transmembrane α-helices in an inward-facing conformation with a core structure of inverted repeats of 5 TM helices (TM2 to TM6 and TM7 to TM11). Galactose is bound in the center of the core, occluded from the outside solutions by hydrophobic residues. The architecture of the core is similar to that of the leucine transporter (LeuT) (
Some bacterial sensor kinases (e.g., 2.A.21.9.1) have N-terminal, 12 TMS, sensor domains that regulate the C-terminal kinase domains. The latter are homologous to the kinase domain of NtrB and other sensor kinases. The N-terminal sensor domains are homologous, but distantly related to members of the SSS. The closest homologues are PutP of E. coli (2.A.21.2.1) and PanF of E. coli (2.A.21.1.1). Homologous regulatory domains are found in Agrobacterium, Mesorhizobium, Sinorhizobium, Vibrio cholerae and Bacillus species. While it is clear that these domains function as sensors, it is not known if they also transport the small molecules they sense.
The generalized transport reaction usually catalyzed by the members of this family is:
solute (out) + nNa+ (out) → solute (in) + nNa+ (in).
An ordered binding model of sodium/substrate transport suggests that sodium binds to the empty transporter first, thereby inducing a conformational alteration which increases the affinity of the transporter for the solute. The formation of the ternary complex induces another structural change that exposes sodium and substrate to the other site of the membrane. Substrate and sodium are released, and the empty transporter re-orientates in the membrane, allowing the cycle to start again.
Proteins belonging to the SSS family can be found in the Transporter Classification Database.
- Sodium/pantothenate symporter InterPro: IPR011849
- Sodium/proline symporter InterPro: IPR011851
- Cation/acetate symporter ActP InterPro: IPR014083
Human proteins containing this domain
- APC Superfamily
- Transporter Classification Database
- Crystal structures:
- Structure of the K294A mutant of vSGLT (2010):
- Crystal Structure of Sodium/Sugar symporter with bound Galactose from vibrio parahaemolyticus (2008):
- Faham S, Watanabe A, Besserer GM, et al. (August 2008). "The crystal structure of a sodium galactose transporter reveals mechanistic insights into Na+/sugar symport". Science. 321 (5890): 810–4. doi:10.1126/science.1160406. PMID 18599740.
- Wong, Foon H.; Chen, Jonathan S.; Reddy, Vamsee; Day, Jonathan L.; Shlykov, Maksim A.; Wakabayashi, Steven T.; Saier, Milton H. (2012-01-01). "The amino acid-polyamine-organocation superfamily". Journal of Molecular Microbiology and Biotechnology. 22 (2): 105–113. doi:10.1159/000338542. ISSN 1660-2412. PMID 22627175.
- Reizer J, Reizer A, Saier Jr MH (1990). "The Na+/pantothenate symporter (PanF) of Escherichia coli is homologous to the Na+/proline symporter (PutP) of E. coli and the Na+/glucose symporters of mammals". Res. Microbiol. 141 (9): 1069–1072. doi:10.1016/0923-2508(90)90080-A. PMID 1965458.
- Reizer J, Reizer A, Saier Jr MH (1994). "A functional superfamily of sodium/solute symporters". Biochim. Biophys. Acta. 1197 (2): 133–136. doi:10.1016/0304-4157(94)90003-5. PMID 8031825.
- Mazier, S; Quick, M; Shi, L (August 19, 2011). "Conserved tyrosine in the first transmembrane segment of solute:sodium symporters is involved in Na+-coupled substrate co-transport.". Journal of Biological Chemistry. 286 (33): 29347–55. doi:10.1074/jbc.M111.263327. PMC . PMID 21705334.
- Perez, C; Ziegler, C (May 2013). "Mechanistic aspects of sodium-binding sites in LeuT-like fold symporters.". Biological Chemistry. 394 (5): 641–8. doi:10.1515/hsz-2012-0336. PMID 23362203.
- Saier, MH Jr. "2.A.21 The Solute:Sodium Symporter (SSS) Family". Transporter Classification Database. Saier Lab Bioinformatics Group and SDSC.
- Quick M1, Loo DD, Wright EM., M; Loo, DD; Wright, EM (January 19, 2001). "Neutralization of a conserved amino acid residue in the human Na+/glucose transporter (hSGLT1) generates a glucose-gated H+ channel.". Journal of Biological Chemistry. 276 (3): 1728–34. doi:10.1074/jbc.m005521200. PMID 11024018.
- Jung, H; Hilger, D; Raba, M (January 1, 2012). "The Na+/L-proline transporter PutP.". Frontiers in Bioscience. 17: 745–59. doi:10.2741/3955. PMID 22201772.
- Jung, H (October 2, 2002). "The sodium/substrate symporter family: structural and functional features.". FEBS. 529 (1): 73–7. doi:10.1016/s0014-5793(02)03184-8. PMID 12354616.
- Faham, S; Watanabe, A; Besserer, GM; Cascio, D; Specht, A; Hirayama, BA; Wright, EM; Abramson, J (August 8, 2008). "The crystal structure of a sodium galactose transporter reveals mechanistic insights into Na+/sugar symport.". Science. 321 (5890): 810–4. doi:10.1126/science.1160406. PMID 18599740.
- Pao, GM; Saier, MH Jr. (February 1995). "Response regulators of bacterial signal transduction systems: selective domain shuffling during evolution.". Journal of Molecular Evolution. 40 (2): 136–54. doi:10.1007/bf00167109. PMID 7699720.
This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.
Sodium:solute symporter family Provide feedback
This family includes P33413 which is not in the Prosite entry. Membership of this family is supported by a significant blast score.
Internal database links
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR001734
Sodium/substrate symport (or co-transport) is a widespread mechanism of solute transport across cytoplasmic membranes of pro- and eukaryotic cells. Thereby the energy stored in an inwardly directed electrochemical sodium gradient (sodium motive force, SMF) is used to drive solute accumulation against a concentration gradient. The SMF is generated by primary sodium pumps (e.g. sodium/potassium ATPases, sodium translocating respiratory chain complexes) or via the action of sodium/proton antiporters. Sodium/substrate transporters are grouped in different families based on sequence similarities [PUBMED:1965458, PUBMED:8031825].
One of these families, known as the sodium:solute symporter family (SSSF), contains over a hundred members of pro- and eukaryotic origin [PUBMED:12354616]. The average hydropathy plot for SSSF proteins predicts 11 to 15 putative transmembrane domains (TMs) in alpha-helical conformation. A secondary structure model of PutP from Escherichia coli suggests the protein contains 13 TMs with the N terminus located on the periplasmic side of the membrane and the C terminus facing the cytoplasm. The results support the idea of a common topological motif for members of the SSSF. Transporters with a C-terminal extension are proposed to have an additional 14th TM.
An ordered binding model of sodium/substrate transport suggests that sodium binds to the empty transporter first, thereby inducing a conformational alteration which increases the affinity of the transporter for the solute. The formation of the ternary complex induces another structural change that exposes sodium and substrate to the other site of the membrane. Substrate and sodium are released and the empty transporter re-orientates in the membrane allowing the cycle to start again.
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Cellular component||membrane (GO:0016020)|
|Molecular function||transporter activity (GO:0005215)|
|Biological process||transport (GO:0006810)|
|transmembrane transport (GO:0055085)|
Below is a listing of the unique domain organisations or architectures in which this domain is found. More...
The graphic that is shown by default represents the longest sequence with a given architecture. Each row contains the following information:
- the number of sequences which exhibit this architecture
a textual description of the architecture, e.g. Gla, EGF x 2, Trypsin.
This example describes an architecture with one
Gladomain, followed by two consecutive
EGFdomains, and finally a single
- a link to the page in the Pfam site showing information about the sequence that the graphic describes
- the UniProt description of the protein sequence
- the number of residues in the sequence
- the Pfam graphic itself.
Note that you can see the family page for a particular domain by clicking on the graphic. You can also choose to see all sequences which have a given architecture by clicking on the Show link in each row.
Finally, because some families can be found in a very large number of architectures, we load only the first fifty architectures by default. If you want to see more architectures, click the button at the bottom of the page to load the next set.
Loading domain graphics...
This large superfamily contains a variety of transporters including amino acid permeases that according to TCDB belong to the APC (Amino acid-Polyamine-organoCation) superfamily.
The clan contains the following 20 members:AA_permease AA_permease_2 AA_permease_C Aa_trans BCCT BenE Branch_AA_trans CstA HCO3_cotransp K_trans MFS_MOT1 Na_Ala_symp Nramp SNF Spore_permease SSF Sulfate_transp Transp_cyt_pur Trp_Tyr_perm Xan_ur_permease
We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the UniProtKB sequence database, the NCBI sequence database, and our metagenomics sequence database. More...
There are various ways to view or download the sequence alignments that we store. We provide several sequence viewers and a plain-text Stockholm-format file for download.
We make a range of alignments for each Pfam-A family:
- the curated alignment from which the HMM for the family is built
- the alignment generated by searching the sequence database using the HMM
- Representative Proteomes (RPs) at 15%, 35%, 55% and 75% co-membership thresholds
- alignment generated by searching the UniProtKB sequence database using the family HMM
- alignment generated by searching the NCBI sequence database using the family HMM
- alignment generated by searching the metagenomics sequence database using the family HMM
You can see the alignments as HTML or in three different sequence viewers:
- a Java applet developed at the University of Dundee. You will need Java installed before running jalview
- an HTML page showing the whole alignment.Please note: full Pfam alignments can be very large. These HTML views are extremely large and often cause problems for browsers. Please use either jalview or the Pfam viewer if you have trouble viewing the HTML version
- an HTML-based representation of the alignment, coloured according to the posterior-probability (PP) values from the HMM. As for the standard HTML view, heatmap alignments can also be very large and slow to render.
You can download (or view in your browser) a text representation of a Pfam alignment in various formats:
You can also change the order in which sequences are listed in the alignment, change how insertions are represented, alter the characters that are used to represent gaps in sequences and, finally, choose whether to download the alignment or to view it in your browser directly.
You may find that large alignments cause problems for the viewers and the reformatting tool, so we also provide all alignments in Stockholm format. You can download either the plain text alignment, or a gzipped version of it.
We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.
1Cannot generate PP/Heatmap alignments for seeds; no PP data available
Key: available, not generated, — not available.
Format an alignment
We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.
You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.
HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...
If you find these logos useful in your own work, please consider citing the following article:
This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.
Note: You can also download the data file for the tree.
Curation and family details
This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.
|Number in seed:||10|
|Number in full:||14837|
|Average length of the domain:||348.50 aa|
|Average identity of full alignment:||18 %|
|Average coverage of the sequence by the domain:||71.62 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 26740544 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||16|
|Download:||download the raw HMM for this family|
Weight segments by...
Change the size of the sunburst
selected sequences to HMM
a FASTA-format file
- 0 sequences
- 0 species
This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the More....
This chart is a modified "sunburst" visualisation of the species tree for this family. It shows each node in the tree as a separate arc, arranged radially with the superkingdoms at the centre and the species arrayed around the outermost ring.
How the sunburst is generated
The tree is built by considering the taxonomic lineage of each sequence that has a match to this family. For each node in the resulting tree, we draw an arc in the sunburst. The radius of the arc, its distance from the root node at the centre of the sunburst, shows the taxonomic level ("superkingdom", "kingdom", etc). The length of the arc represents either the number of sequences represented at a given level, or the number of species that are found beneath the node in the tree. The weighting scheme can be changed using the sunburst controls.
In order to reduce the complexity of the representation, we reduce the number of taxonomic levels that we show. We consider only the following eight major taxonomic levels:
Colouring and labels
Segments of the tree are coloured approximately according to their superkingdom. For example, archeal branches are coloured with shades of orange, eukaryotes in shades of purple, etc. The colour assignments are shown under the sunburst controls. Where space allows, the name of the taxonomic level will be written on the arc itself.
As you move your mouse across the sunburst, the current node will be highlighted. In the top section of the controls panel we show a summary of the lineage of the currently highlighed node. If you pause over an arc, a tooltip will be shown, giving the name of the taxonomic level in the title and a summary of the number of sequences and species below that node in the tree.
Anomalies in the taxonomy tree
There are some situations that the sunburst tree cannot easily handle and for which we have work-arounds in place.
Missing taxonomic levels
Some species in the taxonomic tree may not have one or more of the main eight levels that we display. For example, Bos taurus is not assigned an order in the NCBI taxonomic tree. In such cases we mark the omitted level with, for example, "No order", in both the tooltip and the lineage summary.
Unmapped species names
The tree is built by looking at each sequence in the full alignment for the family. We take the name of the species given by UniProt and try to map that to the full taxonomic tree from NCBI. In some cases, the name chosen by UniProt does not map to any node in the NCBI tree, perhaps because the chosen name is listed as a synonym or a misspelling in the NCBI taxonomy.
So that these nodes are not simply omitted from the sunburst tree, we group them together in a separate branch (or segment of the sunburst tree). Since we cannot determine the lineage for these unmapped species, we show all levels between the superkingdom and the species as "uncategorised".
Since we reduce the species tree to only the eight main taxonomic levels, sequences that are mapped to the sub-species level in the tree would not normally be shown. Rather than leave out these species, we map them instead to their parent species. So, for example, for sequences belonging to one of the Vibrio cholerae sub-species in the NCBI taxonomy, we show them instead as belonging to the species Vibrio cholerae.
Too many species/sequences
For large species trees, you may see blank regions in the outer layers of the sunburst. These occur when there are large numbers of arcs to be drawn in a small space. If an arc is less than approximately one pixel wide, it will not be drawn and the space will be left blank. You may still be able to get some information about the species in that region by moving your mouse across the area, but since each arc will be very small, it will be difficult to accurately locate a particular species.
The tree shows the occurrence of this domain across different species. More...
We show the species tree in one of two ways. For smaller trees we try to show an interactive representation, which allows you to select specific nodes in the tree and view them as an alignment or as a set of Pfam domain graphics.
Unfortunately we have found that there are problems viewing the interactive tree when the it becomes larger than a certain limit. Furthermore, we have found that Internet Explorer can become unresponsive when viewing some trees, regardless of their size. We therefore show a text representation of the species tree when the size is above a certain limit or if you are using Internet Explorer to view the site.
If you are using IE you can still load the interactive tree by clicking the "Generate interactive tree" button, but please be aware of the potential problems that the interactive species tree can cause.
For all of the domain matches in a full alignment, we count the number that are found on all sequences in the alignment. This total is shown in the purple box.
We also count the number of unique sequences on which each domain is found, which is shown in green. Note that a domain may appear multiple times on the same sequence, leading to the difference between these two numbers.
Finally, we group sequences from the same organism according to the NCBI code that is assigned by UniProt, allowing us to count the number of distinct sequences on which the domain is found. This value is shown in the pink boxes.
We use the NCBI species tree to group organisms according to their taxonomy and this forms the structure of the displayed tree. Note that in some cases the trees are too large (have too many nodes) to allow us to build an interactive tree, but in most cases you can still view the tree in a plain text, non-interactive representation. Those species which are represented in the seed alignment for this domain are highlighted.
You can use the tree controls to manipulate how the interactive tree is displayed:
- show/hide the summary boxes
- highlight species that are represented in the seed alignment
- expand/collapse the tree or expand it to a given depth
- select a sub-tree or a set of species within the tree and view them graphically or as an alignment
- save a plain text representation of the tree
Please note: for large trees this can take some time. While the tree is loading, you can safely switch away from this tab but if you browse away from the family page entirely, the tree will not be loaded.
There is 1 interaction for this family. More...
We determine these interactions using iPfam, which considers the interactions between residues in three-dimensional protein structures and maps those interactions back to Pfam families. You can find more information about the iPfam algorithm in the journal article that accompanies the website.
For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the SSF domain has been found. There are 6 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
Loading structure mapping...