This family consists of several eukaryotic Organic-Anion-Transporting Polypeptides (OATPs). Several have been identified mostly in human and rat. Different OATPs vary in tissue distribution and substrate specificity. Since the numbering of different OATPs in particular species was based originally on the order of discovery, similarly numbered OATPs in humans and rats did not necessarily correspond in function, tissue distribution and substrate specificity (in spite of the name, some OATPs also transport organic cations and neutral molecules). Thus, Tamai et al. [1] initiated the current scheme of using digits for rat OATPs and letters for human ones. Prostaglandin transporter (PGT) proteins (e.g. Swiss:Q92959) are also considered to be OATP family members. In addition, the methotrexate transporter OATK (Swiss:P70502) is closely related to OATPs. This family also includes several predicted proteins from Caenorhabditis elegans and Drosophila melanogaster. This similarity was not previously noted. Note: Members of this family are described (in the Swiss-Prot database) as belonging to the SLC21 family of transporters.

1: Molecular identification and characterization of novel members of the human organic anion transporter (OATP) family. Tamai I, Nezu J, Uchino H, Sai Y, Oku A, Shimane M, Tsuji A; Biochem Biophys Res Commun 2000;273:251-260. PMID:10873595