Olfactory Receptors (ORs) are the physical barriers between the environment and the brain. ORs are members of the GPCR-rhodopsin family, which is involved in cell recognition, signal transduction activation, and sense mediation. OR is made up of seven transmembrane (TM) helical domains bound by three putative extracellular loops (EL) and three putative intracellular loops (IL), an extracellular N-terminus, and an intracellular C-terminus. At the intersection of TM3 and IL2, the intracellular loop includes a conserved sequence motif, the aspartate-arginine-tyrosine (DRY) amino acid motif, which is a hallmark of GPCRs. The TM1, TM2, and TM7 are all conserved. The binding site specificity is determined by the amino acid side chains of the central TM domains, which are structurally diverse. The binding pocket of ORs has a hydrophobic environment, indicative of hydrophobic interactions between odorants and ORs. The binding specificity of ORs is influenced not only by the central TM-domains hyper-variable region, but also by the N-termini and C-termini. Both terminals are small, with only about 20 amino acids each. The conserved cysteine residues in the EL1 and EL2-loops are involved in inter- and intramolecular disulphide linkages. One of the three cysteine restudies in EL2-loop has a specific role. A metal binding site is formed by the sequence motif (HXXC[DE]) in EL2-loop. On binding with Zn(II) or Cu, the EL2-loop transforms into a -helical structure confirmation (eighth helix) (II).When an odorant with a high affinity for metal ions replaces one of the metal-ligated amino acids in the EL2-loop, ORs undergo structural rearrangement, which is necessary for the activation of G-olf proteins attached to OR receptors. On the cytoplasmic side of the TM domains, the sequence motifs KAFSTC, PMYFFL, and YRDYAM play a role in OR folding and activation. The amino acid residues on the extracellular side of TM domains are variable, indicating a wide range of possible odorant recognition sites.

OlfactionBase lists 2067 ORs from two species (Human (851) and Mus musculus (1216)).

Sr. No Receptor Organism Length Chromosome Family Sub Family UniProt GenBank #Odorants Details
226 OR4F2P Human 11 4 F NG_004259 0 View
227 OR4F3 Human 312 5 4 F Q6IEY1 NM_001005224 0 View
228 OR4F4 Human 305 15 4 F Q96R69 NM_001004195 0 View
229 OR4F5 Human 305 1 4 F Q8NH21 NM_001005484 0 View
230 OR4F6 Human 312 15 4 F Q8NGB9 NM_001005326 0 View
231 OR4F7P Human 6 4 F NG_004682 0 View
232 OR4F8P Human 19 4 F NG_004359 0 View
233 OR4G11P Human 1 4 F NG_004423 0 View
234 OR4G1P Human 19 4 G NG_004133 0 View
235 OR4G2P Human 15 4 G NG_003201 0 View
236 OR4G3P Human 19 4 G NG_003222 0 View
237 OR4G4P Human 1 4 G NG_004148 0 View
238 OR4G6P Human 15 4 G NG_004268 0 View
239 OR4H12P Human 14 4 H NG_004089 0 View
240 OR4H6P Human 15 4 H NG_002185 0 View
241 OR4K1 Human 311 14 4 K Q8NGD4 NM_001004063 0 View
242 OR4K11P Human 21 4 K NG_004161 0 View
243 OR4K12P Human 21 4 K NG_004160 0 View
244 OR4K13 Human 304 14 4 K Q8NH42 KP290328 0 View
245 OR4K14 Human 310 14 4 K Q8NGD5 NM_001004712 0 View
246 OR4K15 Human 348 14 4 K Q8NH41 NM_001005486 0 View
247 OR4K16P Human 14 4 K NG_004172 0 View
248 OR4K17 Human 315 14 4 K Q8NGC6 KP290449 0 View
249 OR4K2 Human 314 14 4 K Q8NGD2 KP290650 0 View
250 OR4K3 Human 315 14 4 K Q96R72 KP290323 0 View
Showing 226 to 250 of total 2067 entries