Members of the organic solute transporter (OST) family (TC# 2.A.82) (Slc51 genes) have been characterized from a small bottom feeding species of fish called the little skate, Raja erinacea.
[7] OSTαβ proteins are made in a variety of tissues including the small intestine, colon, liver, biliary tract, kidney, and adrenal gland.
In polarized epithelial cells, they are localized to the basolateral membrane and function in the export or uptake of bile acids and steroids.
[8] Homologues of OSTα are found in many eukaryotes including animals (both vertebrates and invertebrates), plants, fungi and slime molds.
However, bioinformatics utilizing combinations of homology modelling and mutation experiments have been used to explore the heterdimer nature of the system as well as the mechanisms of substrate recognition and transport.