Crystal structure of aphrodisin, a sex pheromone from female hamster11Edited by R Huber

Abstract : We have solved the crystal structure of aphrodisin, a pheromonal protein inducing a copulatory behaviour in male hamster, using MAD methods with selenium, at 1.63 A Ê resolution. The monomeric protein belongs to the lipocalin family, and possesses a disul®de bridge in a loop between strands 2 and 3. This disul®de bridge is characteristic of a family of lipocalins mainly identi®ed in rodents, and is analogous to the ®fth disul®de bridge of the long neurotoxins, such as alpha cobratoxin. An elongated electron density was found inside the buried cavity, which might represent a serendipitous ligand of unknown origin. The analysis of the water accessible surfaces of the side-chains bordering the cavity indicates that Phe76 may be the door for the natural ligand to access the cavity. This residue de®nes the entry of the cavity as belonging to the consensus for lipocalins. The face bearing Phe76 might also serve for the interaction with the receptor.