C6ORF192 Forms a Unique Evolutionary Branch Among Solute Carriers (SLC16, SLC17, and SLC18) and Is Abundantly Expressed in Several Brain Regions

About one third of all known human proteins are membrane proteins, which constitute several large families. The solute carriers with over 300 known members are probably the second largest family with additional members frequently being identified. We recently found a new putative solute carrier, C6ORF192, belonging to the major facilitator superfamily type of proteins. The gene is evolutionary highly conserved with a single copy present in each of the genomes from mouse, rat, chicken, zebrafish, tetraodon, Caenorhabditis elegans, and Drosophila melanogaster. C6ORF192 forms a novel evolutionary branch of solute carriers and is most closely related to the solute carrier families 16, 17, and 18, all members of the major facilitator superfamily. Ten of the 25 members of these families show amino acid identity with C6ORF192 ranging from 21% to 27%. C6ORF192 differs however, structurally from these families and does not share key motifs in the transmembrane domains. Expression profiling by quantitative real-time polymerase chain reaction and in situ hybridization showed that C6ORF192 transcript can be detected in several tissues, both in the central nervous system and the periphery.