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https://bar.utoronto.ca/thalemine/service/ is incorrect| Description | Bicarbonate (HCO 3-) 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 HCO 3-transport modes. Anion exchanger proteins exchange HCO 3-for Cl -in a reversible, electroneutral manner [ ]. Na+/HCO 3-co-transport proteins mediate the coupled movement of Na +and HCO 3-across plasma membranes, often in an electrogenic manner [ ]. Na+driven Cl -/HCO 3-exchange and K +/HCO 3-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 HCO 3-transporters that have been cloned to date (the anion exchangers and Na +/HCO 3-co-transporters) reveals that they are homologous. This is not entirely unexpected, given that they both transport HCO 3-and are inhibited by a class of pharmacological agents called disulphonic stilbenes [ ]. 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.Anion exchange proteins participate in pH and cell volume regulation. They are glycosylated, plasma-membrane transport proteins that exchange hydrogen carbonate (HCO 3-) for chloride (Cl -) in a reversible, electroneutral manner [ , ]. To date three anion exchanger isoforms have been identified (AE1-3), AE1 being the previously-characterised erythrocyte band 3 protein. They share a predicted topology of 12-14 transmembrane (TM) domains, but have differing distribution patterns and cellular localisation. The best characterised isoform, AE1, is known to be the most abundant membrane protein in mature erythrocytes. It has a molecular mass of ~95kDa and consists of two major domains. The N-terminal 390 residues form a water-soluble, highly elongated domain that serves as an attachment site for the binding of the membrane skeleton and other cytoplasmic proteins. The remainder of the protein is a 55kDa hydrophobic domain that is responsible for catalysing anion exchange. The function of the analogous domains of AE2 and AE3 remains to be determined [].Naturally-occurring mutations have been characterised in the AE1 gene, which give rise to forms of several human diseases: included are spherocytosis, affecting red blood cells, and familial distal renal tubular acidosis, a kidney disease associated with the formation of kidney stones [ ].This entry represents two conserved small regions of approximately 11 and 14 residues found in AE1-3 mostly from chordates. The first region contains four clustered positive charged residues and is located just before the first transmembrane segment from the integral domain. The second region contains a lysine, which is the covalent binding site for the isothiocyanate group of DIDS, an inhibitor of anion exchange. | Name | Anion exchange, conserved site |
| Short Name | Anion_exchange_CS | Type | Conserved_site |
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