Hormone binding alters the conformation of the insulin receptor.

Fat cells or fat cell membranes were briefly subjected to mild proteolysis under conditions where insulin receptors were either free or bound to (125)I-labeled insulin. When receptors were then affinity-labeled to visualize the effects of this treatment, it was observed that receptors that had been occupied by ligand during proteolysis exhibited greater rates of degradation than unoccupied receptors. These results demonstrate that insulin-receptor interaction induces a change in receptor structure that may be related to signal transmission.