Setmelanotide anti-obesity drug, molecular mode

Molecular model of a molecule of the anti-obesity drug setmelanotide binding to a melanocortin 4 (MC4) receptor, an example of a G-protein-coupled receptor (GPCR), and triggering a signalling cascade. MC4 receptors are found in the hypothalamus of the brain. They are crucial for appetite regulation, energy homeostasis and body-weight control. Binding of setmelanotide to MC4 causes the alpha subunit of the G-protein to exchange its bound molecule of GDP (guanosine triphosphate) for a molecule of GTP (guanosine triphosphate) and to be released from the GPCR. The G-alpha subunit binds to the enzyme adenylyl cyclase (blue), activating it. Adenylyl cyclase catalyses the conversion of ATP (adenosine triphosphate) to cyclic adenosine monophosphate (cAMP) and pyrophosphate (red). cAMP regulates numerous cell functions., Photo by JUAN GAERTNER/SCIENCE PHOTO LIBRARY