We identified the major autophosphorylation sites in the insulin receptor and correlated their
phosphorylation with the phosphotransferase activity of the receptor on synthetic peptides.
The receptor, purified from Fao hepatoma cells on immobilized wheat germ agglutinin,
undergoes autophosphorylation at several tyrosine residues in its beta-subunit; however,
anti-phosphotyrosine antibody (alpha-PY) inhibited most of the phosphorylation by trapping
the initial sites in an inactive complex. Exhaustive trypsin digestion of the inhibited beta …