Binds to bile acids and is involved in enterohepatic bile acid metabolism. Required for efficient apical to basolateral transport of conjugated bile acids in ileal enterocytes (By similarity). Stimulates gastric acid and pepsinogen secretion. Found exclusively in the ileum and to a lesser extent in distal jejunum. Forms a beta-barrel structure that accommodates the hydrophobic ligand in its interior. Can bind at least two ligands per molecule, however, the stoichiometry is debated. Belongs to the calycin superfamily. Fatty-acid binding protein (FABP) family.