Covalent labeling of the hepatic glucagon receptor

The procedure for covalently labeling the hepatic glucagon receptor utilizes the light-sensitive heterobifunctional cross-linker hydroxysuccinimidyl-p-azidobenzoate (HSAB) to link the bound [125I-Tyr10]monoiodoglucagon ([125I]MIG) to the receptor protein. The method involves first the binding of the labeled hormone to its receptor and the removal of the excess unbound label. This is followed by incubation with the cross-linker, in the dark and then under ultraviolet illumination to covalently couple the bound [125I]MIG. HSAB contains an amino reactive group as well as an aryl azide which, upon light activation, is converted to an aryl nitrene that reacts in a chemically unspecific manner