|View/Edit Human||View/Edit Mouse|
|solute carrier family 4 (anion exchanger), member 1, adapter protein|
|Locus||Chr. 2 p23.3|
Band 3 anion transport protein is a phylogenetically-preserved transport protein responsible for mediating the exchange of chloride (Cl−) with bicarbonate (HCO3−) across plasma membranes. Functionally similar members of the AE clade are AE2 and AE3.
Band 3 is present in the basolateral face of the α-intercalated cells of the collecting ducts of the nephron, which are the main acid-secreting cells of the kidney. They generate hydrogen ions and bicarbonate ions from carbon dioxide and water - a reaction catalysed by carbonic anhydrase. The hydrogen ions are pumped into the collecting duct tubule by vacuolar H+ ATPase, the apical proton pump, which thus excretes acid into the urine. kAE1 exchanges bicarbonate for chloride on the basolateral surface, essentially returning bicarbonate to the blood. Here it performs two functions:
- Electroneutral chloride and bicarbonate exchange across the plasma membrane on a one-for-one basis. This is crucial for CO2 uptake by the red blood cell and conversion (by hydration catalysed by carbonic anhydrase) into a proton and a bicarbonate ion. The bicarbonate is then excreted (in exchange for a chloride) from the cell by band 3.
- Physical linkage of the plasma membrane to the underlying membrane skeleton (via binding with ankyrin and protein 4.2). This appears to be to prevent membrane surface loss, rather than being to do with membrane skeleton assembly.
- the erythrocyte (red blood cell) cell membrane and
- the basolateral surface of the alpha-intercalated cell (the acid secreting cell type) in the collecting duct of the kidney.
The erythrocyte isoform of AE1, known as eAE1, is composed of 911 amino acids. eAE1 is an important structural component of the erythrocyte cell membrane, making up to 25% of the cell membrane surface. Each red cell contains approximately one million copies of eAE1.
The kidney isoform of AE1, known as kAE1 (which is 65 amino acids shorter than erythroid AE1) is found in the basolateral membrane of alpha-intercalated cells in the cortical collecting duct of the kidney.
Mutations of kidney AE1 cause distal (type 1) renal tubular acidosis, which is an inability to acidify the urine, even if the blood is too acidic. These mutations are disease causing as they cause mistargetting of the mutant band 3 proteins so that they are retained within the cell or occasionally addressed to the wrong (i.e. apical) surface.
More importantly erythroid AE1 mutations cause 15–25% of cases of Hereditary spherocytosis (a disorder associated with progressive red cell membrane loss), and also cause the hereditary conditions of Hereditary stomatocytosis and Southeast Asian Ovalocytosis
AE1 was discovered following SDS-PAGE ( sodium dodecyl sulfate polyacrylamide gel electrophoresis ) of erythrocyte cell membrane. The large 'third' band on the electrophoresis gel represented AE1, which was thus initially termed 'Band 3'.
- "Diseases that are genetically associated with SLC4A1 view/edit references on wikidata".
- "Human PubMed Reference:".
- "Mouse PubMed Reference:".
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- Tanner MJ (1993). "Molecular and cellular biology of the erythrocyte anion exchanger (AE1)". Semin. Hematol. 30 (1): 34–57. PMID 8434259.
- Chambers EJ, Askin D, Bloomberg GB, Ring SM, Tanner MJ (1998). "Studies on the structure of a transmembrane region and a cytoplasmic loop of the human red cell anion exchanger (band 3, AE1)". Biochem. Soc. Trans. 26 (3): 516–20. PMID 9765907.
- Inaba M (2002). "[Band 3: expanding knowledge on its functions]". Seikagaku. 73 (12): 1431–5. PMID 11831035.
- Tanner MJ (2002). "Band 3 anion exchanger and its involvement in erythrocyte and kidney disorders". Curr. Opin. Hematol. 9 (2): 133–9. doi:10.1097/00062752-200203000-00009. PMID 11844997.
- Shayakul C, Alper SL (2004). "Defects in processing and trafficking of the AE1 Cl−/HCO3− exchanger associated with inherited distal renal tubular acidosis". Clin. Exp. Nephrol. 8 (1): 1–11. doi:10.1007/s10157-003-0271-x. PMID 15067510.
- Diego blood group system at BGMUT Blood Group Antigen Gene Mutation Database at NCBI, NIH
- Band 3 Protein at the US National Library of Medicine Medical Subject Headings (MeSH)
- Chloride-Bicarbonate Antiporters at the US National Library of Medicine Medical Subject Headings (MeSH)