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
301 OR5AU1 Human 362 14 5 AU Q8NGC0 NM_001004731 0 View
302 OR5AW1P Human 5 AW NG_004158 0 View
303 OR5AZ1P Human 11 5 AZ NG_004207 0 View
304 OR5B10P Human 11 5 B NG_002306 0 View
305 OR5B12 Human 314 11 5 B Q96R08 NM_001004733 0 View
306 OR5B15P Human 11 5 B NG_004206 0 View
307 OR5B17 Human 314 11 5 B Q8NGF7 NM_001005489 2 View
308 OR5B19P Human 11 5 B NG_004205 0 View
309 OR5B1P Human 11 5 B NG_002305 0 View
310 OR5B2 Human 309 11 5 B Q96R09 NM_001005566 0 View
311 OR5B21 Human 309 11 5 B A6NL26 NM_001005218 0 View
312 OR5B3 Human 314 11 5 B Q8NH48 NM_001005469 0 View
313 OR5BA1P Human 11 5 BA NG_004204 0 View
314 OR5BB1P Human 11 5 BB NG_004203 0 View
315 OR5BC1P Human 11 5 BC NG_004202 0 View
316 OR5BD1P Human 11 5 BD NG_002253 0 View
317 OR5BE1P Human 11 5 BE NG_004201 0 View
318 OR5BH1P Human 5 BH NG_004157 0 View
319 OR5BJ1P Human 12 5 BJ NG_004156 0 View
320 OR5BK1P Human 12 5 BK NG_004391 0 View
321 OR5BL1P Human 11 5 BL NG_004200 0 View
322 OR5BM1P Human 3 5 BM NG_004145 0 View
323 OR5BN1P Human 11 5 BN NG_004199 0 View
324 OR5BN2P Human 11 5 BN NG_004864 0 View
325 OR5BP1P Human 11 5 BP NG_004198 0 View
Showing 301 to 325 of total 2067 entries