Summary

HCO3- transporter family

This family contains Band 3 anion exchange proteins that exchange CL-/HCO3- such as P48751. This family also includes cotransporters of Na+/HCO3- such as O15153.

InterPro entry IPR011531

Bicarbonate (HCO₃^-) transport mechanisms are the principal regulators of pH in animal cells. Such transport also plays a vital role in acid-base movements in the stomach, pancreas, intestine, kidney, reproductive organs and the central nervous system. Functional studies have suggested four different HCO₃^- transport modes. Anion exchanger proteins exchange HCO₃^- for Cl^- in a reversible, electroneutral manner PUBMED:2289848. Na⁺/HCO₃^- co-transport proteins mediate the coupled movement of Na⁺ and HCO₃^- across plasma membranes, often in an electrogenic manner PUBMED:. Na^- driven Cl^-/HCO₃^- exchange and K⁺/HCO₃^- exchange activities have also been detected in certain cell types, although the molecular identities of the proteins responsible remain to be determined.

Sequence analysis of the two families of HCO₃^- transporters that have been cloned to date (the anion exchangers and Na⁺/HCO₃^- co-transporters) reveals that they are homologous. This is not entirely unexpected, given that they both transport HCO₃^- and are inhibited by a class of pharmacological agents called disulphonic stilbenes PUBMED:9235899. They share around ~25-30% sequence identity, which is distributed along their entire sequence length, and have similar predicted membrane topologies, suggesting they have ~10 transmembrane (TM) domains.

This domain is found at the C-terminus of many bicarbonate transport proteins. It is also found in some plant proteins responsible for boron transport PUBMED:12447444. In these proteins it covers almost the entire length of the sequence.

Clan

This family is a member of clan APC (CL0062), which contains the following 16 members:

AA_permease Aa_trans BenE Branch_AA_trans CbiQ CstA DUF1468 HCO3_cotransp Na_Ala_symp Nramp Spore_permease SSF Sulfate_transp Transp_cyt_pur Trp_Tyr_perm Xan_ur_permease

Gene Ontology

Cellular component	integral to membrane (GO:0016021)
Molecular function	anion exchanger activity (GO:0015380)
Biological process	anion transport (GO:0006820)

Internal database links

SCOOP:

EcsB Tmemb_55A

External database links

MIM:	112050 130600 112010
PANDIT:	PF00955
PRINTS:	PR00165
PROSITE:	PDOC00192
SCOP:	1btr
SYSTERS:	HCO3_cotransp
Transporter classification:	2.A.31

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Alignments

There are various ways to view or download the sequence alignments that we store. You can use a sequence viewer to look at either the seed or full alignment for the family, or you can look at a plain text version of the sequence in a variety of different formats. More...

View options

Alignment:	Seed (18) Full (597) NCBI (1321) Metagenomics (18)
Viewer:

Formatting options

Alignment:	Seed (18) Full (597)
Format:
Order:	Tree Alphabetical
Sequence:	Inserts lower case All upper case
Gaps:
Download/view:	Download View

Download options

Very large alignments can often cause problems for the formatting tool above. If you find that downloading or viewing a large alignment is problematic, you can also download a gzip-compressed, Stockholm-format file containing the seed or full alignment for this family.

You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

The main seed and full alignments are generated using sequences from the UniProt sequence database. However, we also generate alignments using sequences from the NCBI sequence database and the "metaseq" metagenomics dataset.

You can view alignments from these two additional datasets using the form above, or you can download alignments of NCBI or metagenomics sequences, as gzip-compressed files.

Pfam alignments:	Seed (18) Full (597) NCBI (1321) Metagenomics (18)
Full length sequences	Full-sequences (597)

External links

MyHits provides a collection of tools to handle multiple sequence alignments. For example, one can refine a seed alignment (sequence addition or removal, re-alignment or manual edition) and then search databases for remote homologs using HMMER2.

HMM logo

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...

Trees

This page displays the phylogenetic tree for this family. 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 or full alignments.

Note: You can also download the data files for the seed, full, NCBI or metagenomics trees.

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.

Curation

Seed source:

Pfam-B_1004 (release 3.0)

Previous IDs:

Anion_Exchanger;

Type:

Family

Author:

Croning MDR, Finn RD, Bateman A

Number in seed:

18

Number in full:

597

Average length of the domain:

282.60 aa

Average identity of full alignment:

27 %

Average coverage of the sequence by the domain:

35.67 %

HMM information

HMM build commands:

build method: hmmbuild -o /dev/null HMM SEED

search method: hmmsearch -Z 9421015 -E 1000 HMM pfamseq

Model details:

Parameter	Sequence	Domain
Gathering cut-off	19.7	19.7
Trusted cut-off	20.0	22.2
Noise cut-off	17.8	19.0

Model length:

510

Family (HMM) version:

14

Download:

download the raw HMM for this family

Species distribution

Tree controls

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The tree shows the occurrence of this domain across different species. More...

Species trees

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.

Interactive tree

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

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Structures

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 HCO3_cotransp domain has been found.

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Family: HCO3_cotransp (PF00955)

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