Revisiting the odorant-binding protein LUSH of Drosophila melanogaster: evidence for odour recognition and discrimination.

LUSH is a soluble odorant-binding protein of the fruit fly Drosophila melanogaster. Mutants not expressing this protein have been reported to lack the avoidance behaviour, exhibited by wild type flies, to high concentrations of ethanol. Very recently, the three-dimensional structure of LUSH complexed with short-chain alcohols has been resolved supporting a role for this protein in binding and detecting small alcohols. Here we report that LUSH does not bind ethanol and that wild type flies are in fact attracted by high concentrations of ethanol. We also report that LUSH binds some phthalates and that flies are repelled by such compounds. Finally, our fluorescence data, interpreted in the light of the three-dimensional structure of LUSH, indicate that the protein undergoes a major conformational change, similar to that reported for the pheromone-binding protein of Bombyx mori, but triggered, in our case, by ligand.