Solubilization of the pig ileal intrinsic factor receptor with papain treatment and studies on the solubilized receptor.

The intrinsic factor receptor, known to consist of two subunits alpha and beta, has been solubilized by papain digestion from porcine small intestine. Papain liberates a part of the outermost subunit (alpha) of the receptor. The solubilized part was called papain-alpha. It was purified by affinity chromatography on Sepharose-vitamin B-12-intrinsic factor gel and its molecular dimensions were measured. Its molecular weight measured with SDS-polyacrylamide gel electrophoresis is 45000, its isoelectric point is 4.2 and it binds the cobalamin-intrinsic factor complex in the same way as the whole receptor.