Molecular Mechanism of Agonism and Inverse Agonism in the Melanocortin Receptors
Among the rhodopsin-like 7TM receptors, the MC receptors are functionally unique because their high constitutive signaling activity is regulated not only by endogenous peptide agonistsMSH peptidesbut also by endogenous inverse agonists, namely, the proteins agouti and AGRP. Moreover, the metal-ion Zn2+ increases the signaling activity of at least the MC1 and MC4 receptors in three distinct ways
7tm receptor constitutive signaling agouti agrp metal-ion zn2+ mc4 zinc alpha-msh receptor activation