Essential component of the Ost-alpha/Ost-beta complex, a heterodimer that acts as the intestinal basolateral transporter responsible for bile acid export from enterocytes into portal blood. Efficiently transports the major species of bile acids (taurocholate) (By similarity). Taurine conjugates are transported more efficiently across the basolateral membrane than glycine-conjugated bile acids (By similarity). Can also transport steroids such as estrone 3-sulfate and dehydroepiandrosterone 3-sulfate, therefore playing a role in the enterohepatic circulation of sterols (By similarity). Able to transport eicosanoids such as prostaglandin E2 (By similarity). taurocholate(out) = taurocholate(in) estrone 3-sulfate(out) = estrone 3-sulfate(in) dehydroepiandrosterone 3-sulfate(out) = dehydroepiandrosterone 3-sulfate(in) tauroursodeoxycholate(out) = tauroursodeoxycholate(in) glycoursodeoxycholate(out) = glycoursodeoxycholate(in) glycocholate(out) = glycocholate(in) taurochenodeoxycholate(out) = taurochenodeoxycholate(in) glycochenodeoxycholate(out) = glycochenodeoxycholate(in) taurodeoxycholate(out) = taurodeoxycholate(in) glycodeoxycholate(out) = glycodeoxycholate(in) prostaglandin E2(out) = prostaglandin E2(in) Interacts with SLC51B. The Ost-alpha/Ost-beta complex is a heterodimer composed of alpha (SLC51A) and beta (SLC51B) subunit (By similarity). Transported from the endoplasmic reticulum to the plasma membrane upon interacting with SLC51B. Mainly restricted to the lateral and basal membranes of ileal enterocytes (By similarity). Belongs to the OST-alpha family.