CNGA3
Domain
The C-terminal coiled-coil domain mediates homotrimerization of CNGA subunits.
The cyclic nucleotide-binding domain (CNBD) comprises three helices and a beta-roll of eight beta-strands from CNGA3 and CNGB3 subunits. Upon cNMP binding transmits the conformational changes to the C-linker domain of the S6 helix to open the ion conduction pathway.
The ion conduction pathway consists of S5, S6 and pore helices from CNGA3 and CNGB3 subunits. It contains a central hydrophobic gate that opens upon cNMP binding.
Function
Pore-forming subunit of the cone cyclic nucleotide-gated channel. Mediates cone photoresponses at bright light converting transient changes in intracellular cGMP levels into electrical signals. In the dark, cGMP levels are high and keep the channel open enabling a steady inward current carried by Na(+) and Ca(2+) ions that leads to membrane depolarization and neurotransmitter release from synaptic terminals. Upon photon absorption cGMP levels decline leading to channel closure and membrane hyperpolarization that ultimately slows neurotransmitter release and signals the presence of light, the end point of the phototransduction cascade (PubMed:10888875, PubMed:12815043, PubMed:34969976, PubMed:37463923). Pore-forming subunit of the gustatory cyclic nucleotide-gated channel. In the taste buds, may sense oral extracellular pH and conduct ion currents that modulate the excitability of taste cells (By similarity). Conducts cGMP- and cAMP-gated ion currents, with permeability for monovalent and divalent cations (By similarity) (PubMed:12815043).
Involvement in disease
Achromatopsia 2
ACHM2
An autosomal recessive, ocular stationary disorder due to the absence of functioning cone photoreceptors in the retina. It is characterized by total colorblindness, low visual acuity, photophobia and nystagmus.
None
The disease is caused by variants affecting the gene represented in this entry.
Sequence Similarities
Belongs to the cyclic nucleotide-gated cation channel (TC 1.A.1.5) family. CNGA3 subfamily.
Tissue Specificity
Prominently expressed in retina.
Cellular localization
- Cell membrane
- Multi-pass membrane protein
Alternative names
CNCG3, CNGA3, Cyclic nucleotide-gated channel alpha-3, CNG channel alpha-3, CNG-3, CNG3, Cone photoreceptor cGMP-gated channel subunit alpha-3