[The role of GTP-binding proteins in the olfactory reception of vertebrates].

The inhibitory effect of the non-hydrolyzable GTP analog Gpp (NH) p (10(-5)-10(-3) M) on the specific binding of some natural odorants (L-3H-amino acids, boar sex pheromone analog 5 alpha-3H-androstan-3-one) and sex hormones (17 beta-3H-estradiol, 3H-testosterone and 5 alpha-3H-dihydrotestosterone) to the olfactory receptors of some vertebrates (fish, frog, sow, rat) was found. Under the same experimental conditions Gpp (NH) p did not affect the high affinity binding of 5 alpha-3H-androstan-3-one to the sow respiratory tissue preparations. It was assumed that the changes in the specific binding of odorants in the presence of guanyl nucleotides can be a suitable test for the identification of true odorant receptors which conjugate with the system of olfactory transduction through G-proteins. The existence of two forms of high affinity GTPase in the olfactory tissue was demonstrated. One of them is an integral membrane component, whereas the second one is a loosely bound to the membrane and it can be solubilized in the presence of EDTA. The role of G-proteins in the system of olfactory transduction and the problem of odorant receptor identification are discussed.