Essential component of the Ost-alpha/Ost-beta complex, a heterodimer that acts as the intestinal basolateral transporter responsible for the translocation of bile acids (such as taurocholate), steroids (such as estrone sulfate), and eicosanoids (such as prostaglandin E2). taurocholate(out) = taurocholate(in) prostaglandin E2(out) = prostaglandin E2(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) Interacts with slc51b. The Ost-alpha/Ost-beta complex is a heterodimer composed of alpha (slc51a) and beta (slc51b) subunit (By similarity). Belongs to the OST-alpha family.