Cyclic nucleotide-gated (CNG) channels are crucial for visual and olfactory transductions (PMID: 12432397). Native CNG channels are heterotetramers composed of homologous A and B subunits. The olfactory CNG channels are composed of two CNGA2 subunits, one CNGA4 and one CNGB1b subunit, each containing a cyclic nucleotide-binding domain (PMID: 22786723). CNGA2, also named as CNCA, CNCA1 and CNCG2, is the primary subunit of the olfactory CNG channel. Odorant signal transduction is probably mediated by a G-protein coupled cascade using cAMP as second messenger. Activation of olfactory channel by cyclic nucleotides leads to a depolarization of olfactory sensory neurons.