Sulphydryl groups and the quinone receptor in insect olfaction and gustation

Abstract

UNDERSTANDING of energy-transduction aspects of olfactory messenger–receptor interactions has been lacking¹, until the recent advances^2–6 made using the chemoreceptor protein for quinone messengers, isolated from sensory nerve membranes in the antennae of Periplaneta americana^7,8. Availability of this protein for in vitro experiment has filled a void that existed, for several decades, between the behavioural and electrophysiological experimental capabilities in this field. With purified receptor protein available, physicochemical aspects of olfaction and gustation have become amenable to direct experiment. Here we present evidence that messenger naphthoquinones showed marked selectivity for the receptor protein when it was exposed in vitro to a saturating 10⁻⁴ M concentration of each messenger in the presence of the other Triton-solubilised proteins from the insect's antennae. The electrophoretically resolved^4,7,8 receptor-containing band only constituted approximately 13.7% of the protein in the Triton-soluble fraction, but it bound more than 75% of radiolabelled messengers. The other messenger-associated radioactivity was retained at the origin of the gels or was scattered as low level DPMs among the several other resolved bands. These findings also confirm earlier experimental results⁸ on the selective binding of messenger to the receptor band as resolved in 3.5% acrylamide gels.