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
2001 MOR253-8 Mus musculus 318 13 A Q8VGJ4 NM_146934 0 View
2002 MOR274-1 Mus musculus 315 2 T Q3B877 NM_147027 0 View
2003 MOR188-2 Mus musculus 312 8 K Q8VGS7 NM_147019 0 View
2004 MOR185-1 Mus musculus 315 8 J Q7TR71 NM_147078 5 View
2005 MOR160-2 Mus musculus 308 8 S Q8VF93 NM_146457 0 View
2006 MOR156-5 Mus musculus 320 1 O Q8VFA1 NM_146465 0 View
2007 MOR190-2 Mus musculus 316 8 K Q7TR74 NM_146391 0 View
2008 MOR228-4 Mus musculus 309 4 X Q7TQY9 NM_146263 0 View
2009 MOR184-1 Mus musculus 308 5 K A0A140T8K4 NM_147002 3 View
2010 MOR251-1 Mus musculus 309 13 A Q8VGT4 NM_147026 2 View
2011 MOR186-1 Mus musculus 346 8 K A2AVX9 AY318251 0 View
2012 MOR186-2 Mus musculus 313 8 K Q8VGS6 NM_147018 0 View
2013 MOR183-4 Mus musculus 307 5 H Q7TS46 NM_146397 0 View
2014 MOR182-6 Mus musculus 305 Q7TS34 NM_207551 0 View
2015 MOR245-13 Mus musculus 311 4 G Q8VF29 NM_146381 0 View
2016 MOR231-18 Mus musculus 318 4 A A2AUA2 NM_146373 0 View
2017 MOR202-20 Mus musculus 317 5 B Q8VFK3 NM_146575 0 View
2018 MOR32-2 Mus musculus 312 52 E L7N1Y4 NM_147070 0 View
2019 MOR130-1 Mus musculus 313 1 AB Q7TRY0 NM_146338 0 View
2020 MOR259-7P Mus musculus 10 AK NG_001840 0 View
2021 MOR253-11P Mus musculus 13 A NG_002087 0 View
2022 MOR183-7P Mus musculus 309 5 H Q7TS43 NM_001011791 0 View
2023 MOR265-1 Mus musculus 314 10 U Q7TS26 NM_146269 0 View
2024 MOR190-4P Mus musculus 313 Q7TR73 NG_017472 0 View
2025 MOR192-2 Mus musculus 313 8 K Q7TR65 NM_207135 0 View
Showing 2001 to 2025 of total 2067 entries