Chemosensory proteins from the proboscis of Mamestra brassicae

Soluble, low molecular weight proteins were immunodetected in proboscis ext racts of Mamestra brassicae males by Western blot, using antibodies raised against the general odorant-binding protein of the moth Antheraea polyphemu s. The same antibodies weakly labelled the sensillum lymph and subcuticular space of sensilla styloconica on ultrathin sections of the proboscis. The morphology of sensilla styloconica is described. The immunodetected protein s yielded several N-terminal sequences, three of which showed strong affini ty for tritiated analogues of pheromonal com pounds of M. brassicae in bind ing assays. The cDNAs coding for these sequences were cloned and it was sho wn that the new proteins are related to the OS-D protein of Drosophila. The y are named chemosensory proteins (CSP-MbraA1-CSP-MbraA5 and CSP-MbraB1 and CSP-MbraB2) and may have an odorant-binding protein-like function. A commo n localization in both olfaction and taste organs suggests a physiological role depending on the cellular environment.