Cloning and expression of a cDNA encoding the transporter of taurine and beta-alanine in mouse brain

A taurine/beta-alanine transporter was cloned from a mouse brain cDNA library by screening with a partial cDNA probe of the glycine transporter at low stringency. The deduced amino acid sequence predicts 590 amino acids with typical characteristics of the sodium-dependent neurotransmitter transporters such as sequence homology and membrane topography. However, the calculated isoelectric point of the taurine/beta-alanine transporter is more acidic (pI = 5.98) than those (pI > 8.0) of other cloned neurotransmitter transporters. Xenopus oocytes injected with cRNA of the cloned transporter expressed uptake activities with Km = 4.5 microM for taurine and Km = 56 microM for beta-alanine. Northern hybridization showed a single transcript of 7.5 kilobases that was highly enriched in kidney and distributed evenly in various parts of the brain. In situ hybridization showed the mRNA of the taurine/beta-alanine transporter to be localized in the corpus callosum, striatum, and anterior commisure. Specific localization of the taurine/beta-alanine transporter in mouse brain suggests a potential function for taurine and beta-alanine as neurotransmitters.