The many faces of proinsulin

Marcoullis, G. &; Gräsbeck, R. Vitamin B₁₂-Binding Proteins in Human Gastric Mucosa. General Pattern and Demonstration of Intrinsic Factor Isoproteins Typical of Mucosa. Scand. J. din. Lab. Invest. 35, 5–11, 1975.

Extracts of human stomach mucosa were shown to contain immunoreactive intrinsic factor and small amounts of R protein and transcobalamin 11. In gel filtration the mucosal vitamin B₁₂-intrinsic factor complex behaved as though its molecular weight were smaller than the corresponding complex in gastric juice. In isoelectric focusing both the gastric juice and mucosal vitamin B₁₂-intrinsic factor complexes resolved into numerous isoproteins. These findings were verified by DEAE-cellulose chromatography. The mucosal intrinsic factor isoprotein pattern contained, in addition to the isoproteins found in gastric juice, components with higher isoelectric points that is, pH 5.73–6.64.