TAUT Proteins

Taurine (2-aminoethanesulfonic acid) is a major intracellular amino acid in mammals. It is involved in a number of important physiologic processes, including bile acid conjugation in hepatocytes, modulation of calcium flux and neural excitability, osmoregulation, detoxification, and membrane stabilization. The cells of most organisms respond to hypertonicity by the intracellular accumulation of high concentrations of small organic solutes (osmolytes) that, in contrast to high concentrations of electrolytes, do not perturb the function of macromolecules. The renal medulla is normally the only tissue in mammals that undergoes wide shifts in tonicity. Its hypertonicity when the kidney is excreting a concentrated urine is fundamental to water conservation. The taurine content of the renal medulla of rats infused with 5% NaCl is higher than that in controls, suggesting that taurine behaves as an osmolyte in the renal medulla. Indeed, taurine functions as an osmolyte in Madin-Darby canine kidney (MDCK) cells. When MDCK cells cultured in isotonic medium are switched to hypertonic medium, their content of taurine doubles through the taking up of taurine from the medium. Taurine transport in these cells is dependent on sodium and chloride ions and is localized primarily in the basolateral plasma membrane (summary by Uchida et al., 1992 [PubMed 1518851]).[supplied by OMIM, Jan 2011].