A key step in insects' sense of smell has been uncovered by researchers in Switzerland, the United States and Japan. The discovery could lead to insecticides that stop insects from communicating through chemical signals.
Using nuclear magnetic resonance (NMR), the researchers showed how a protein in an insect's antenna picks up chemical signals called pheromones, then changes its shape to eject them precisely onto sensitive nerve endings.
Many insects depend on pheromones to communicate with each other, whether searching for food or finding a mate, said University of California, Davis, entomologist Walter Leal, who collaborated in the project.
"One could design new compounds that fit in the binding pocket of the protein, but cannot be ejected. This would prevent the insect from detecting other chemical signals," Leal said. These insects would not be able to survive without their sense of smell, he said.
Insects "smell" with their antennae. Pheromone-binding proteins (PBP) pick up pheromones at pores in the outside of the antenna and carry them through a watery layer to the nerve endings, where they are released.
The new NMR results showed that the PBP changes its shape to eject the pheromone molecule. The shape change is triggered by a drop in pH when the PBP-pheromone complex reaches the nerve endings.
The study by Reto Horst, Kurt Wuethrich and colleagues at the Eidgenoessische Technische Hochschule in Zurich, Switzerland, together with UC Davis' Leal and scientists at the National Institute of Agrobiological Sciences in Tsubuka, Japan, is published in the Dec. 4 issue of Proceedings of the National Academies of Sciences of the United States of America.
Editor's note: An animation of pheromone transport is available at http://chemecol.ucdavis.edu/animations/ PBP1_w_sound.html. Images of the proteins with and without pheromone binding are also available. Contact Andy Fell for details.
Proceedings of the National Academy of Sciences