Olfactory receptor classes

Freitag J., Krieger J., Strotmann J. and Breer H. (1995) Two classes of olfactory receptors in Xenopus laevis. Neuron 15, 1383-1392. 

Vogt R. G., Prestwich G. D. and Lemer M. R. (1991a) Odorant-binding-protein subfamilies associate with distinct classes of olfactory receptor neurons in insects. J. Neurobiol. 22, 74-84. 

Sklar P. B., Anholt R. H. and Snyder S. H. (1986) The odorant sensitive adenylate cyclase of olfactory receptor cells differential stimulation by distinct classes of odorants. J. Biol. Chem. 261, 15538-15543. 

The ability to insert active olfactory receptors into functioning cells means that it is now possible to profile the activity of receptor proteins and move from the realm of guesswork into experimental reality. For example, Sanz et al. have profiled and compared the selectivity of two human olfactory receptors that belong to different phylogenetic classes (62). They found that the class I receptor, OR52D1 has a relatively narrow range, which accepts alcohols, esters, ketones, and acids with a... 

Sanz G,Schlegel C, Pernollet J-C, Briand L. Comparison of odorant specificity of two human olfactory receptors from different phylogenetic classes and evidence for antagonism. Chem. Senses 2005 30 69-80. 

The knowledge of chemosensory communication has grown rapidly over the last ten years since the identification of the first olfactory receptor genes. The subsequent cloning of genes for rodent vomeronasal receptors, which are important in pheromone detection, has revealed an unexpected diversity of around 250 receptors belonging to two structurally different classes. 

The TAAR Gene Family - the Second Class of Olfactory Receptor Gene Family... 

Fig. 1 The four olfactory receptor gene families. ORs, ORAs, and TAARs belong to the class A of GPCRs, with a short N-terminus and a ligand binding site within the TM domains, whereas OlfCs are class C GPCRs, similar to the metabotropic glutamate receptor, with the ligand binding pocket in the large N-terminal extracellular domain...

The 5-HT2 receptor class has three subtypes 5-HT2, 5-HT2g, and 5-HT2(r all couple to pertussis toxin-insensitive G proteins (e.g., and G j) and link to activation of phospholipase C. 5-HT2 receptors are enriched in forebrain regions such as the neocortex and olfactory tubercle, as well as in several nuclei arising from the brainstem. The 5-HT2(j receptor, similar in sequence and pharmacology to the 5-HT2 receptor, is expressed abundantly in the choroid plexus, where it may modulate CSFproduction (see Chapter 11). 

The location of the olfactory receptors is in the place (at the top of the cavity) where it is most likely that incoming chemical molecules will strike the surface. When chemical molecules do contact receptors, they must fit together before a nervous signal can be generated. This requires that the receptor must have a shape complementary to the shape of the chemical in order that the two join together. Each different class of chemicals generally has a different set of receptors sensitive to that chemical class. The form of the nasal passage and the form of the receptors are both determined by their functions. 

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