olfactory receptor activity

Definition

Target type: molecularfunction

Combining with an odorant and transmitting the signal from one side of the membrane to the other to initiate a change in cell activity in response to detection of smell. [GOC:bf, GOC:dph, GOC:sart, PMID:19135896, PMID:21041441]

Olfactory receptor activity refers to the ability of a protein, specifically an olfactory receptor, to bind to and detect odorant molecules. These receptors, located in the olfactory epithelium of the nasal cavity, are responsible for the sense of smell. They are G protein-coupled receptors (GPCRs), meaning they initiate a signal transduction cascade upon binding to odorants.

Here is a detailed description of the molecular function of olfactory receptor activity:

1. **Odorant Binding:** Odorant molecules, volatile compounds in the air, diffuse into the nasal cavity and bind to the extracellular domain of olfactory receptors. This binding is highly specific, with each receptor typically recognizing a small range of odorants.

2. **Activation of G Protein:** Binding of an odorant molecule to the receptor triggers a conformational change in the receptor protein. This change activates a G protein, a heterotrimeric complex composed of alpha, beta, and gamma subunits.

3. **Production of Second Messenger:** The activated alpha subunit of the G protein dissociates from the beta and gamma subunits and activates adenylyl cyclase, an enzyme that catalyzes the conversion of ATP to cyclic AMP (cAMP). cAMP is a second messenger that acts as a signal inside the olfactory sensory neuron.

4. **Opening of Ion Channels:** cAMP binds to and activates cyclic nucleotide-gated (CNG) ion channels, allowing the influx of sodium and calcium ions into the olfactory sensory neuron.

5. **Depolarization of Neuron:** The influx of positive ions causes depolarization of the neuron, generating an electrical signal. This signal is transmitted to the olfactory bulb in the brain via the olfactory nerve.

6. **Signal Amplification:** The olfactory receptor signaling pathway involves multiple amplification steps, contributing to the sensitivity of the olfactory system. This includes the activation of multiple G protein molecules by a single receptor and the production of multiple cAMP molecules by a single activated adenylyl cyclase.

7. **Signal Termination:** The olfactory signal is terminated by the hydrolysis of cAMP by phosphodiesterase and the deactivation of the G protein.

8. **Diversity of Receptors:** The human olfactory system contains hundreds of different olfactory receptor genes, each encoding a receptor protein with a distinct odorant-binding specificity. This diversity allows for the detection of a wide range of odorants and the discrimination of different smells.

9. **Adaptation:** Prolonged exposure to an odorant leads to a decrease in the response of olfactory neurons, a phenomenon known as adaptation. This mechanism allows the olfactory system to adapt to constant background odors and focus on changes in odorant concentrations.

Overall, olfactory receptor activity is a complex process involving a cascade of molecular events that convert odorant binding into electrical signals, enabling the perception of smell.'
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Proteins (1)

Compounds (18)