Bicarbonate transporter protein
HCO3- transporter family | |||||||||
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![]() a low energy structure for the final cytoplasmic loop of band 3, nmr, minimized average structure
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Identifiers | |||||||||
Symbol | HCO3_cotransp | ||||||||
Pfam | PF00955 | ||||||||
Pfam clan | CL0062 | ||||||||
InterPro | IPR011531 | ||||||||
PROSITE | PDOC00192 | ||||||||
SCOP | 1btr | ||||||||
SUPERFAMILY | 1btr | ||||||||
TCDB | 2.A.31 | ||||||||
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Band 3 cytoplasmic domain | |||||||||
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![]() crystal structure of the cytoplasmic domain of human erythrocyte band-3 protein
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Identifiers | |||||||||
Symbol | Band_3_cyto | ||||||||
Pfam | PF07565 | ||||||||
Pfam clan | CL0340 | ||||||||
InterPro | IPR013769 | ||||||||
SCOP | 1hyn | ||||||||
SUPERFAMILY | 1hyn | ||||||||
TCDB | 2.A.31 | ||||||||
OPM superfamily | 336 | ||||||||
OPM protein | 1btq | ||||||||
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In molecular biology, bicarbonate transporter proteins are proteins which transport bicarbonate. 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.[1] Na+/HCO3 − co-transport proteins mediate the coupled movement of Na+ and HCO3 − across plasma membranes, often in an electrogenic manner.[2] 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.[3] 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.
A conserved domain is found at the C terminus of many bicarbonate transport proteins. It is also found in some plant proteins responsible for boron transport.[4] In these proteins it covers almost the entire length of the sequence.
The Band 3 anion exchange proteins that exchange bicarbonate are the most abundant polypeptide in the red blood cell membrane, comprising 25% of the total membrane protein. The cytoplasmic domain of band 3 functions primarily as an anchoring site for other membrane-associated proteins. Included among the protein ligands of this domain are ankyrin, protein 4.2, protein 4.1, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphofructokinase, aldolase, hemoglobin, hemichromes, and the protein tyrosine kinase (p72syk).[5]
References
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This article incorporates text from the public domain Pfam and InterPro IPR011531 This article incorporates text from the public domain Pfam and InterPro IPR013769