Odorant signal transduction is probably mediated by a G-protein coupled cascade using cAMP as second messenger. The olfactory channel can be shown to be activated by cyclic nucleotides which leads to a depolarization of olfactory sensory neurons. Heterotetramer composed of two subunits of CNGA2, one of CNGA4 and one of CNGB1b. The complex forms the cyclic nucleotide-gated (CNG) channel of olfactory sensory neurons (By similarity). Olfactory neurons. The C-terminal coiled-coil domain mediates trimerization of CNGA subunits. The olfactory channel is activated by both cAMP and cGMP at similar concentrations, whereas the cGMP-gated channel is much less sensitive to cAMP. Belongs to the cyclic nucleotide-gated cation channel (TC 1.A.1.5) family. CNGA2 subfamily.