CNGA1
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 CNGA1 and CNGB1 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 CNGA1 and CNGB1 subunits. It contains a central hydrophobic gate that opens upon cNMP binding.
Function
Pore-forming subunit of the rod cyclic nucleotide-gated channel. Mediates rod photoresponses at dim 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. Conducts cGMP- and cAMP-gated ion currents, with permeability for monovalent and divalent cations. The selectivity for Ca(2+) over Na(+) increases with cGMP concentrations, whereas the selectivity among monovalent ions is independent of the cGMP levels.
Sequence Similarities
Belongs to the cyclic nucleotide-gated cation channel (TC 1.A.1.5) family. CNGA1 subfamily.
Tissue Specificity
Expressed in the retina, in rod cells (at protein level).
Cellular localization
- Cell membrane
- Multi-pass membrane protein
Alternative names
CNCG, CNCG1, Cyclic nucleotide-gated channel alpha-1, CNG channel alpha-1, CNG-1, CNG1, Cyclic nucleotide-gated cation channel 1, Rod photoreceptor cGMP-gated cation channel subunit alpha, cGMP-gated cation channel alpha-1