Max-Planck-Institut für Verhaltensphysiologie, 82319 Seewiesen/Starnberg, Germany.
A kinetic model of perireceptor and receptor events (computerized by J. Thorson, Oxford)
has been developed for olfactory sensilla of the moth Antheraea polyphemus.
The reaction network includes the adsorptive uptake of pheromone molecules by the olfactory
hairs, the diffusion of the pheromone molecules pheromone from the hair surface to the
receptor cell, the formation of a complex of pheromone (F) and the pheromone binding
protein, with its reduced form (Bred), and its oxidized form (Box),
the interaction of this complex with receptor molecules (R) on the plasma membrane of the
olfactory cell, the deactivation of the pheromone, and finally its enzymatic degradation. The
model is consistent with morphometrical, radiometrical, electrophysiological and biochemical
data. It includes the following assumptions:
- only the complex FBred activates the receptor molecules,
- the observed redox shift FBred --> FBox deactivates the
pheromone molecules,
- the redox shift is catalyzed by the receptor molecules,
- pheromone molecules bound to PBP are largely, but not fully protected from enzymatic degradation,
- the dendritic membrane area is maximally covered with receptor molecules, and
- the duration of the elementary receptor potentials elicited by single pheromone molecules
reflects the lifetime of the ternary complex FBredR.
The study suggests that perireceptor and receptor events govern the kinetics of the receptor potential.