The insect attractant 1-octen-3-ol is the natural ligand of bovine odorant-binding protein

Bovine odorant-binding protein (bOBP) is a dimeric lipocalin present in lar ge amounts in the respiratory and olfactory nasal mucosa, The structure of bOBP refined at 2.0-Angstrom resolution revealed an elongated volume of ele ctron density inside each buried cavity, indicating the presence of one (or several) naturally occurring copurified ligand(s) (Tegoni et al. (1996) Na t, Struct. Biol, 3, 863-867; Bianchet ct al, (1996) Nat, Struct, Biol. 3, 9 34-939), In the present work, by combining mass spectrometry, x-ray crystal lography (1.8-Angstrom resolution), and fluorescence, it has been unambiguo usly established that natural bOBP contains the racemic form of 1-octen-3-o l. This volatile substance is a typical component of bovine breath and in g eneral of odorous body emanations of humans and animals. The compound 1-oct en-3-ol is also an extremely potent olfactory attractant for many insect sp ecies, including some parasite vectors like Anopheles, (Plasmodium) or Glos sina (Trypanosoma), For the first time, a function can be assigned to an OB P, with a possible role of bOBP in the ecological relationships between bov ine and insect species.