The human body consists of trillions of cells that constantly communicate with one another. A central role in this communication process is played by receptor proteins on the cell surface. Since they often serve as drug targets, they have been the subject of intensive research. Often there are whole families of receptors. The signal messengers as well as the receptors are very similar, so it is not clear how the signals are distinguished from one another at the molecular level. Now, in a joint research project, scientists from Collaborative Research Centre 1423 at Leipzig University, the Hangzhou Institute for Advanced Study and the Chinese Academy of Sciences in Shanghai have succeeded in determining high-resolution structures for three related signaling complexes that occur naturally in the body for the neuropeptide Y (NPY) receptor family, thus shedding light on the small but essential differences. The researchers have now published their new findings in the journal Science Advances.