Chemosensory Mechanism in American Cockroach Olfaction and Gustation

• Published in: Nature (London) 1973-08, Vol.244 (5415), p.370-371
• Main Authors: ROZENTAL, JACK M, NORRIS, DALE M
• Format: Article
• Language: English
• Subjects: Humanities and Social Sciences; letter; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/244370a0

ALTHOUGH numerous theories of olfaction and gustation 1–8 have been published, there is little experimental evidence on the energy-transfer mechanisms involved in the interactions of chemical messengers with proteinaceous receptors of sensory neurones. One such mechanism, involved in the inhibition of feeding of Periplaneta americana and Scolytus multistriatus by various 1,4-naphthoquinones, has been extensively studied and partially interpreted behaviourally 9–16 , ultrastructurally 10–16 , electrophysiologically 10–16 and biochemically 10–16 . These messenger naphthoquinones were shown to act through a selective reaction with sulphydryl 10–16 groups in a particular membrane-associated receptor macromolecule which was proven to be physically accessible in situ 17 to these chemicals through cuticular pores and tubules 10–16 in the walls of chemoreceptor sensillae on the insect's antennae. This specific energy transfer resulted in disulphide-bond formation or thiol complexing 10–16 , both of which are proven 18 mechanisms in certain proteins for causing conformational changes. Such changes can alter the cationic permeability of macromolecules composing membranes 18 . The messenger-altered cation permeability of the receptor thus can result in the generation of action potentials in the sensory neurone 10–16 . Here we report certain physicochemical characteristics of the messenger-naphthoquinone receptor protein interactions as analysed in a deoxygenated system at physiological p H by the in vitro technique of dropping mercury electrode (DME) polarography (PO4 ‘Polariter’, London Co.). The polarogram is a current–voltage curve obtained by applying a gradually increasing voltage to a system and measuring the current flow at each potential. Characteristic polarographic half-wave potential (that is, E ½) values for proteins were attributed exclusively to exposed, reactive sulphydry 1 , or reducible disulphide, groups 19–22 . In our own investigations, the ‘Triton’ X-100-solubilized quinone-reactive receptor protein from the cockroach antennae gave a characteristic E ½ of −1,860 mV. A control (non-quinone receptor) protein system composed of the saline-soluble proteins from the same antennae gave an E ½ of −1,800 mV. Adding messenger 5-hydroxy-1,4-naphthoquinone (5 × 10 −5 M) in the receptor preparation characteristically shifted the E ½ from −1,860 to −1,880 mV; another less repellent, or feeding-inhibitory, messenger, 2-methyl-1,4-naphthoquinone (5 × 10 −5 M),