Olfactory epithelial protein

The proteins coded for by these genes in vertebrates are G protein-coupled receptors (GPCRs). They are linear chains of amino acids that span the olfactory epithelial membrane in which they are embedded seven times. They act by transmitting the odorant signal to specific olfactory G proteins, Goif. 

The olfactory epithelium is composed of basal, neuronal (olfactory), and susten-tacular (support) cells (Figure 27.3). The portion of each olfactory cell that responds to the olfactory chemical stimuli is the cilia. The odorant substance first diffuses into the mucus that covers the cilia and then binds to specific receptor proteins in the membrane of each cilium. Next, receptor activation by the odorant activates a multiple molecules of the G-protein complex in the olfactory epithelial cell. This, in turn, activates adenylyl cyclase inside the olfactory cell membrane, which, in turn, causes formation of a greater multitude of cAMP molecules. Finally, the cAMP molecules trigger the opening of yet an even greater multitude of sodium ion channels. This amplification mechanism accounts for the exquisite sensitivity of the olfactory neurons to extremely small amounts of odorant. The olfactory epithelium is an important target of certain inhaled toxicants. Certain metals, solvents, proteins, and viruses are transported to the brain via transport from the olfactory epithelium to the olfactory tract and exert neurotoxicity. 

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