The olfactory system can screen thousands of volatile compounds through olfactory receptors. Most of these G-coupled receptors are orphaned, and the molecular basis of the early combinatorial coding of odors is yet to be elucidated. Such an assessment is critical for humans. In this report, we have focused on the odorant profile of OR 17-210 (OR1E3P), a human chemoreceptor binding an odorant binding protein and responsive to cyclic ketones with carbon chain lengths of 8 to 13 carbon atoms. Efficacy of this OR binding with ketones has been estimated based on the abundant expression of this receptor in the baculovirus/ insect system. Computational derived models of this receptor have also been recently published. OR17-210-excitatory ligands displayed monophasic or biphasic dose response curves; such structure-activity relationships are indicative of two groups of odorants that are structurally different. Odorant-binding efficacy could be further related to the G-protein coupling status of the receptor based on the co-expression of the OR with or without a Gα16 protein. Accordingly, it has been proposed that structurally related agonists may differentially recruite OR 17-210 binding sites as a function of their concentration and transduce post-binding signaling through preferred G-protein coupling.
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