The NBCs mediate the movement of 1 Na + and 1вЂ“3 HCO 3 в€’ ions. Three AEs, AE1 (also known as Band 3 of human red blood cells), AE2 and AE3 are found in mammalian tissues (Alper et al., 2002). The AEs mainly mediate Na + independent exchange of Cl в€’ and HCO 3 в€’ across the plasma membrane, although some reports show that they can also transport OH в€’ or SO 4 2в€’ (Jennings, 1976). These are Cl в€’/HCO 3 в€’ exchangers (anion exchangers, AE), Na +/HCO 3 в€’ cotransporters (NBC) and sodium driven Cl в€’/HCO 3 в€’ exchangers (NDCBE/NCBE). Within this family, there are three major categories of proteins, designated by their function. In human cells, these transporters are encoded by ten genes grouped into solute carrier family 4 members 1вЂ“11, excluding number 6, (SLC4A1вЂ“11 Romero et al., 2004). The regulation of intracellular HCO 3 в€’ levels is governed by the HCO 3 в€’ transporter family of proteins that carry HCO 3 в€’ ions, along with at least one monoatomic ion, across the plasma membrane (Romero et al., 2004). It also is involved in regulation of membrane depolarization, cell volume, HCl secretion by the gastric epithelium and NaCl reabsorption by epithelia (Boron, 2001). Western immunoblots and immunoflourescence show that Sp-NBC is concentrated in the flagellar plasma membrane, suggesting a role in motility regulation.Д«icarbonate (HCO 3 в€’) is a crucial ion for intracellular pH regulation in virtually all cells. A neighbor-joining tree shows that Sp-NBC branches closer to the electroneutral type of HCO 3 в€’ transporters. This is characteristic for Na +/HCO 3 в€’ cotransporters, but not for anion exchangers, suggesting that the sea urchin protein is a Na +/HCO 3 в€’ cotransporter. The sea urchin protein possesses a relatively long 3rd extracellular loop with four conserved cysteine residues. It has longer N- and C-terminal cytoplasmic domains compared to human HCO 3 в€’ transporters. The sea urchin protein shares the major structural features of HCO 3 в€’ transporters, including 13 transmembrane segments, a DIDS (4,4-diiodothiocyanatostilbene-2, 2-disulfonic acid) binding motif and N-linked glycosylation sites.

The most similar human protein is the Na +/HCO 3 в€’ cotransporter-2 (NBC2), which has 53% identity and 68% similarity to the sea urchin protein. The annotated protein coding region of the transporter gene consists of 24 exons. The deduced protein is 1214 amino acids and has a calculated molecular mass of 135В kDa. Here we describe the first cloning and localization of a HCO 3 в€’ transporter from sperm of the sea urchin, Strongylocentrotus purpuratus. Bicarbonate (HCO 3 в€’ ) transporters play crucial roles in cell-signaling pathways and are essential for cell viability.

Make alignments macvector