A large-molecular-weight proinsulin-immunoreactive protein fraction was obtained from an extract of fetal bovine pancreases by gel filtration in 6 M guanidine- 1 M acetic acid. Concanavalin A-Sepharose-affinity column chromatography of the large-molecular-weight fraction yielded a discrete α-methyl-mannoside-displaceable immunoreactive peak that also displayed Nacetylglucosamine- specific binding to wheat germ lectin- Sepharose. Chemically tritiated and radioiodinated lectin-reactive proteins interacted specifically with antibodies to insulin and bovine proinsulin. Immunochemically purified (reaction with antibodies followed by separation of antigen-antibody complexes on protein A-Sepharose) radiolabeled lectin-reactive proteins were analyzed by gel filtration in guanidine-acetic acid and by sodium dodecyl sulfate polyacrylamide gel electrophoresis after disulfide bond-cleavage treatments. Results from these studies suggest the existence of an ∼67,000-Mr glycoprotein that contains antigenic domains common to proinsulin and insulin.

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Copyright © 1987 by the American Diabetes Association
1987