A PUTATIVE LIPOPHILIC STIMULANT CARRIER PROTEIN COMMONLY FOUND IN THETASTE AND OLFACTORY SYSTEMS - A UNIQUE MEMBER OF THE PHEROMONE-BINDING PROTEIN SUPERFAMILY

In chemosensory systems, a variety of lipophilic ligand-binding protei ns have been found in saliva or nasal mucus. Lipophilic stimulants rea ch the receptor membrane, carried by these proteins. An acidic 14-kDa protein purified in the blowfly, Phormia regina, belongs to the insect pheromone-binding protein superfamily, but unlike other lipohilic lig and-binding proteins in insect or vertebrate chemosensory systems, it was distributed in both taste and olfactory organs. A similar protein was also isolated in Drosophila melanogaster. Considering their distri butions, cDNA sequences and structural features, we concluded that the se proteins belong to a unique subfamily whose members have convergent ly evolved for a common function required for both senses of taste and olfaction. By an electrophysiological experiment using antiserum, we also suggested that these proteins carry fragrant components of natura l foods in taste systems as well as in olfactory systems.