| Structural highlights
Disease
[S4A4_HUMAN] Autosomal recessive proximal renal tubular acidosis. The disease is caused by mutations affecting the gene represented in this entry. Loss of interaction with and stimulation by CA4 is the cause of retinitis pigmentosa type 17 (RP17).
Function
[S4A4_HUMAN] Electrogenic sodium/bicarbonate cotransporter with a Na(+):HCO3(-) stoichiometry varying from 1:2 to 1:3. May regulate bicarbonate influx/efflux at the basolateral membrane of cells and regulate intracellular pH.[1] [2] [3] [4] [5] [6] [7] Isoform 2: May have a higher activity than isoform 1.[8]
Publication Abstract from PubMed
Na(+)-coupled acid-base transporters play essential roles in human biology. Their dysfunction has been linked to cancer, heart, and brain disease. High-resolution structures of mammalian Na(+)-coupled acid-base transporters are not available. The sodium-bicarbonate cotransporter NBCe1 functions in multiple organs and its mutations cause blindness, abnormal growth and blood chemistry, migraines, and impaired cognitive function. Here, we have determined the structure of the membrane domain dimer of human NBCe1 at 3.9 A resolution by cryo electron microscopy. Our atomic model and functional mutagenesis revealed the ion accessibility pathway and the ion coordination site, the latter containing residues involved in human disease-causing mutations. We identified a small number of residues within the ion coordination site whose modification transformed NBCe1 into an anion exchanger. Our data suggest that symporters and exchangers utilize comparable transport machinery and that subtle differences in their substrate-binding regions have very significant effects on their transport mode.
CryoEM structure of the human SLC4A4 sodium-coupled acid-base transporter NBCe1.,Huynh KW, Jiang J, Abuladze N, Tsirulnikov K, Kao L, Shao X, Newman D, Azimov R, Pushkin A, Zhou ZH, Kurtz I Nat Commun. 2018 Mar 2;9(1):900. doi: 10.1038/s41467-018-03271-3. PMID:29500354[9]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Choi I, Romero MF, Khandoudi N, Bril A, Boron WF. Cloning and characterization of a human electrogenic Na+-HCO-3 cotransporter isoform (hhNBC). Am J Physiol. 1999 Mar;276(3 Pt 1):C576-84. PMID:10069984
- ↑ Sun XC, Bonanno JA. Identification and cloning of the Na/HCO(3-) cotransporter (NBC) in human corneal endothelium. Exp Eye Res. 2003 Sep;77(3):287-95. PMID:12907161
- ↑ Demirci FY, Chang MH, Mah TS, Romero MF, Gorin MB. Proximal renal tubular acidosis and ocular pathology: a novel missense mutation in the gene (SLC4A4) for sodium bicarbonate cotransporter protein (NBCe1). Mol Vis. 2006 Apr 10;12:324-30. PMID:16636648
- ↑ Shirakabe K, Priori G, Yamada H, Ando H, Horita S, Fujita T, Fujimoto I, Mizutani A, Seki G, Mikoshiba K. IRBIT, an inositol 1,4,5-trisphosphate receptor-binding protein, specifically binds to and activates pancreas-type Na+/HCO3- cotransporter 1 (pNBC1). Proc Natl Acad Sci U S A. 2006 Jun 20;103(25):9542-7. doi:, 10.1073/pnas.0602250103. Epub 2006 Jun 12. PMID:16769890 doi:https://dx.doi.org/10.1073/pnas.0602250103
- ↑ Suzuki M, Vaisbich MH, Yamada H, Horita S, Li Y, Sekine T, Moriyama N, Igarashi T, Endo Y, Cardoso TP, de Sa LC, Koch VH, Seki G, Fujita T. Functional analysis of a novel missense NBC1 mutation and of other mutations causing proximal renal tubular acidosis. Pflugers Arch. 2008 Jan;455(4):583-93. doi: 10.1007/s00424-007-0319-y. Epub 2007 , Jul 28. PMID:17661077 doi:https://dx.doi.org/10.1007/s00424-007-0319-y
- ↑ Burnham CE, Amlal H, Wang Z, Shull GE, Soleimani M. Cloning and functional expression of a human kidney Na+:HCO3- cotransporter. J Biol Chem. 1997 Aug 1;272(31):19111-4. PMID:9235899
- ↑ Abuladze N, Lee I, Newman D, Hwang J, Boorer K, Pushkin A, Kurtz I. Molecular cloning, chromosomal localization, tissue distribution, and functional expression of the human pancreatic sodium bicarbonate cotransporter. J Biol Chem. 1998 Jul 10;273(28):17689-95. PMID:9651366
- ↑ Shirakabe K, Priori G, Yamada H, Ando H, Horita S, Fujita T, Fujimoto I, Mizutani A, Seki G, Mikoshiba K. IRBIT, an inositol 1,4,5-trisphosphate receptor-binding protein, specifically binds to and activates pancreas-type Na+/HCO3- cotransporter 1 (pNBC1). Proc Natl Acad Sci U S A. 2006 Jun 20;103(25):9542-7. doi:, 10.1073/pnas.0602250103. Epub 2006 Jun 12. PMID:16769890 doi:https://dx.doi.org/10.1073/pnas.0602250103
- ↑ Huynh KW, Jiang J, Abuladze N, Tsirulnikov K, Kao L, Shao X, Newman D, Azimov R, Pushkin A, Zhou ZH, Kurtz I. CryoEM structure of the human SLC4A4 sodium-coupled acid-base transporter NBCe1. Nat Commun. 2018 Mar 2;9(1):900. doi: 10.1038/s41467-018-03271-3. PMID:29500354 doi:https://dx.doi.org/10.1038/s41467-018-03271-3
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