Decyl-thio-trifluoropropanone, a competitive inhibitor of moth pheromone receptors

An earlier study (Pophof 1998) showed that the esterase inhibit or decyl-th io-trifluoropropano ne inhibited the responses of two receptor neurons of t he moth Antheraea polyphemus tuned to straight-chain pheromone components, an acetate and an aldehyde, respectively. Here we report that decyl-thio-tr ifluoropropanone also inhibited the responses of two pheromone receptor neu rons of Bombyx mori to bombykol and bombykal. In contrast, decyl-thio-trifl uoropropanone activated receptor neurons of the moth Imbrasia cytherea tune d to the pheromone component (Z)-5-decenyl 3-methyl-butanoate. However, dec yl-thio-trifluoropropanone did not affect the responses of two receptor neu rons of B. mori females specialized to the plant volatiles benzoic acid and linalool, respectively. These results indicate that decyl-thio-trifluoropr opanone. besides inhibiting the sensillar esterase, interferes with protein s involved specifically in the excitation of pheromone receptor neurons. In binding studies with radiolabelled decyl-thio-trifluoropropanone, the inhi bitor was bound by the pheromone-binding protein of A. polyphemus. However, the amount of decyl-thio-trifluoropropanone causing response inhibition wa s 300 times lower than the amount of pheromone-binding protein present in t he sensilla. Since the amount of decyl-thio-trifluoropropanone adsorbed cor responded to about the maximum number of receptor molecules calculated per sensillum, we expect that decyl-thio-trifluoropropanone, probably in comple x with pheromone-binding protein, competitively inhibits the pheromone rece ptor molecules.