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
Gene location (Human) Chr. Chromosome 17 (human)[1] Band 17q21.31 Start 44,248,390 bp[1] End 44,268,141 bp[1]
Gene location (Mouse) Chr. Chromosome 11 (mouse)[2] Band 11 66.29 cM|11 D Start 102,239,650 bp[2] End 102,257,029 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in spongy bone bone marrow bone marrow cells renal medulla blood kidney monocyte kidney tubule vena cava glomerulus Top expressed in blood internal carotid artery body of femur external carotid artery yolk sac endocardial cushion spleen belly cord fossa atrium More reference expression data BioGPS 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 disc 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 Species Human Mouse Entrez 6521 20533 Ensembl ENSG00000004939 ENSMUSG00000006574 UniProt P02730 P04919 RefSeq (mRNA) NM_000342 NM_011403 RefSeq (protein) NP_000333 NP_035533 Location (UCSC) Chr 17: 44.25 – 44.27 Mb Chr 11: 102.24 – 102.26 Mb PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

solute carrier family 4 (anion exchanger), member 1, adapter protein
Identifiers
Symbol	SLC4A1AP
NCBI gene	22950
HGNC	13813
OMIM	602655
RefSeq	NM_018158
UniProt	P02730
Other data
Locus	Chr. 2 p23.3
Search for Structures Swiss-model Domains InterPro

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 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]