[Insulin receptors and mechanism of action of insulin and of insulin-like growth factors].

A novel mechanism of activation of the insulin and IGF-I receptors by their respective ligands is proposed, whereby the bivalent ligand bridges the two receptor alpha subunits at opposite sites in a symmetrical receptor structure. The proposed mechanism accounts for the binding stoichiometry and the phenomenon of negative cooperativity. It may play an important role in the regulation of mitogenesis.