Identification of the 14 kDa bile acid transport protein of rat ileal cytosol as gastrotropin.

The 14 kDa bile acid binding protein of rat ileal cytosol (I-BABP), previously shown to be the major intracellular transporter of bile acids in enterocytes, was purified by affinity chromatography and gel electrophoresis. Enzymatic digestion of I-BABP which had been electroblotted to nitrocellulose led to the recovery and sequence analysis of four peptides representing 47 residues of sequence (approximately 35% of the full sequence). All the peptide sequences displayed high levels of identity (greater than 60%) and homology (greater than 80%) to the sequences of porcine and canine gastrotropin. This high level of homology together with other features of I-BABP identify it as rat gastrotropin, establishing gastrotropin as the major intracellular bile acid carrier of rat enterocytes.