Characterization of a chemically tritiated large molecular weight glucagon immunoreactive protein species by lectin-affinity column chromatography and reaction with anti-glucagon antibodies

High molecular weight glucagon immunoreactive material, obtained by gel-filtration (in the presence of 6 M guanidine hydrochloride) of fetal bovine pancreatic extracts, was tritiated by reductive methylation. Concanavalin-A-Sepharose column chromatography of the radiolabeled preparation yielded a discrete Concanavalin-A-reactive, α-methyl-mannoside-displaceable radioactive peak, coinciding with the glucagon immunoreactive peak. Submission of the Con-A-reactive material to wheat germ agglutinin-Sepharose column chromatography yielded a lectin-reactive, N-acetyl-glucosamine-displaceable radioactive peak, coninciding with the glucagon immunoreactive peak. The tritiated Con-A-reactive component interacted specifically with anti-glucagon antibodies. Sephacryl S-200 gel-filtration (in the presence of guanidine hydrochloride) dissociated a ∼40 kDa radioactive species from the antibody-antigen complex. These data provide direct evidence for the existence of a large molecular weight glycosylated glucagon-related protein species from the fetal bovine pancreas.