The SLC4 family of HCO 3 - transporters.
The SLC4 family consists of ten genes. All appear to encode integral membrane proteins with very similar hydropathy plots-consistent with the presence of 10-14 transmembrane segments. At least eight SLC4 members encode proteins that transport HCO(3)(-) (or a related species, such as CO(3)(2-)) across the plasma membrane. Functionally, these eight proteins fall into two major groups: three Cl-HCO(3) exchangers (AE1-3) and five Na(+)-coupled HCO(3)(-) transporters (NBCe1, NBCe2, NBCn1, NDCBE, NCBE). Two of the Na(+)-coupled HCO(3)(- )transporters (NBCe1, NBCe2) are electrogenic; the other three Na(+)-coupled HCO(3)(-) transporters and all three AEs are electroneutral. At least NDCBE transports Cl(-) in addition to Na(+) and HCO(3)(-). Whether NCBE transports Cl(-)-in addition to Na(+) and HCO(3)(-)-is unsettled. In addition, two other SLC4 members (AE4 and BTR1) do not yet have a firmly established function; on the basis of homology, they fall between the two major groups. A characteristic of many, though not all, SLC4 members is inhibition by 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS). SLC4 gene products play important roles in the carriage of CO(2) by erythrocytes, the absorption or secretion of H(+) or HCO(3)(-) by several epithelia, as well as the regulation of cell volume and intracellular pH.
Romero
Michael F
MF
Departments of Physiology and Biophysics and Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4970, USA. michael.romero@cwru.edu
Fulton
Christiaan M
CM
Boron
Walter F
WF
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D027963:Chloride-Bicarbonate Antiporters / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D006801:Humans; D005810:Multigene Family / Q000502:physiology; D012964:Sodium / Q000378:metabolism; D027982:Sodium-Bicarbonate Symporters / Q000502:physiology*
D001639:Bicarbonates; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D027982:Sodium-Bicarbonate Symporters; D012964:Sodium