Demonstration of two distinct insulin-binding components in solubilized human placental membranes by radioimmunoassay using synthetic peptide and anti-synthetic peptide antibody

Abstract

A peptide corresponding to the 957-980 sequence of human placental insulin receptor precursor (HIRP) was synthesized and antisera were produced against the synthetic peptide. Anti-synthetic HIRP(957-980) serum HIR-27 was proved to cross-react with HIRP-related proteins in solubilized human placental membranes. A radioimmunoassay developed with the antiserum and synthetic peptide HIRP(957-980) enabled us to separate, in combination with gel filtration, two insulin-binding components in solubilized human placental membranes which conceivably correspond to the alpha 2 beta 2 and alpha beta structures of the placental insulin receptor. The two components were shown to be distinct in insulin-binding behavior depending on conditions of pH and ionic strength in the binding assay.