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SLC4A1
Available structures
PDB	Ortholog search: PDBe RCSB
List of PDB id codes
	1BH7, 1BNX, 1BTQ, 1BTR, 1BTS, 1BTT, 1BZK, 1HYN, 3BTB, 2BTA, 2BTB, 4KY9, 4YZF
Identifiers
Aliases	SLC4A1, solute carrier family 4 (anion exchanger), member 1 (Diego blood group), AE1, BND3, CD233, DI, EMPB3, EPB3, FR, RTA1A, SW, WD, WD1, WR, CHC, SAO, SPH4, solute carrier family 4 member 1 (Diego blood group)
External IDs	OMIM: 109270; MGI: 109393; HomoloGene: 133556; GeneCards: SLC4A1; OMA:SLC4A1 - orthologs
Gene location (Human)
Chr.	Chromosome 17 (human)
End	44,268,141 bp
Gene location (Mouse)
Chr.	Chromosome 11 (mouse)
End	102,257,029 bp
RNA expression pattern
	Top expressed in
	trabecular bone; ; bone marrow; ; bone marrow cells; ; renal medulla; ; blood; ; monocyte; ; kidney tubule; ; vena cava; ; glomerulus; ; human kidney;
	Top expressed in
	fetal liver hematopoietic progenitor cell; ; blood; ; tibiofemoral joint; ; human fetus; ; internal carotid artery; ; body of femur; ; external carotid artery; ; yolk sac; ; endocardial cushion; ; spleen;
	More reference expression data
	More reference expression data
Gene ontology
Molecular function	protein homodimerization activity; protein-membrane adaptor activity; chloride transmembrane transporter activity; transporter activity; anion transmembrane transporter activity; bicarbonate transmembrane transporter activity; protein binding; ankyrin binding; inorganic anion exchanger activity; sodium:bicarbonate symporter activity; hemoglobin binding;
Cellular component	integral component of membrane; blood microparticle; membrane; cortical cytoskeleton; plasma membrane; integral component of plasma membrane; basolateral plasma membrane; extracellular exosome; Z discdkac; cytoplasmic side of plasma membrane;
Biological process	anion transport; bicarbonate transport; cellular ion homeostasis; chloride transport; ion transport; regulation of intracellular pH; anion transmembrane transport; chloride transmembrane transport; sodium ion transmembrane transport; transport; glycolytic process; blood coagulation; plasma membrane phospholipid scrambling; negative regulation of urine volume; pH elevation; erythrocyte development; protein localization to plasma membrane;
	Sources:Amigo / QuickGO
Orthologs
	6521
	20533
	ENSG00000004939
	ENSMUSG00000006574
	P02730
	P04919
	NM_000342
	NM_011403
	NP_000333
	NP_035533
	Wikidata
View/Edit Human	View/Edit Mouse

Band 3 anion transport protein, also known as anion exchanger 1 (AE1) or band 3 or solute carrier family 4 member 1 (SLC4A1), is a protein that is encoded by the SLC4A1 gene in humans.

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.^[5]

Function

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, the kidney isoform of AE1, exchanges bicarbonate for chloride on the basolateral surface, essentially returning bicarbonate to the blood. Here it performs two functions:^{[citation needed]}

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 having to do with membrane skeleton assembly.

Distribution

It is ubiquitous throughout the vertebrates. In mammals, it is present in two specific sites:^{[citation needed]}

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.

Gene products

The erythrocyte and kidney forms are different isoforms of the same protein.^[6]

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.^{[citation needed]}

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.^{[citation needed]}

Clinical significance

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.^{[citation needed]}

Mutations of erythroid AE1 affecting the extracellular domains of the molecule may cause alterations in the individual's blood group, as band 3 determines the Diego antigen system (blood group).^{[citation needed]}

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^[7] and Southeast Asian ovalocytosis.^[8]

Interactions

Band 3 has been shown to interact with CA2^[9]^[10]^[11]^[12] and CA4.^[13]

Discovery

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'.^[14]