ABSTRACT
The melanocortin system consists of five seven-transmembrane spanning G-protein coupled (GPCRs) receptors (MC1R-MC5R), the endogenous agonists a-, B- and melanocyte stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), and the endogenous antagonists Agouti and Agouti-related protein (AGRP). Melanocortin agonists are involved in the regulation of feeding behavior and weight omeostasis in mammals. Structure-activity relationships (SAR) have been performed on the endogenous melanocortin receptor agonists and antagonists that have identified ligand amino acid residues implicated as important for receptor binding and stimulation. Knowledge of putative ligand-receptor interactions may help to design molecules as therapeutic agents for the treatment of physiological diseases.