Insulin binding modes

Chromodulin, first described in the 1980s, has been isolated firom liver, kidney, and other tissues in several species of experimental animals. Its proposed mode of action is (1) the inactive insulin receptors on cell membranes are converted to an active form by binding circulating insulin (2) this binding... 

G proteins get their name because they bind GTP as part of their effect An example is the G protein that is linked to the epinephrine receptor and leads to the production of cAMP as a second messenger. Receptor tyrosine kinases have a different mode of action. When they bind their hormone, they phos-phorylate tyrosine residues on themselves and other target proteins, which then act as a second messenger. Insulin is an example of a hormone that binds to a receptor tyrosine kinase. 

Membrane-bound hormone receptors were detected in the late 1960s. The binding of insulin, glucagon, and epinephrine to isolated plasma membranes of the rat liver or to isolated fat cells and fat cell membranes has been reported (Tomasi et al., 1970 Rodbell et al., 1971 Cuatrecasas, 1971a,b Freychet et al., 1971 Dunnick and Marinetti, 1971). Species-specific interaction between growth hormones and erythrocyte membranes has been shown by Cambiaso et al. (1971). Lef-kowitz et al. (1971) have published a detailed description of the interaction of adrenocorticotropic hormone with its receptors in the adrenal cortex, which appears to be a membrane-associated interaction (Finn et al., 1972). The modes of action for polypeptide hormones and their receptors have been the subject of intense investigation, and a number of reviews on this subject have been published (Cuatrecasas, 1974 Kahn, 1975 Catt and Dufau, 1977). 

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