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Description

cGMP-gated cation channel alpha-1 (UniProt: Q00194, also known as Cyclic nucleotide-gated cation channel 1, Cyclic nucleotide-gated channel alpha-1, CNG channel alpha-1, CNG-1, CNG1, Cyclic nucleotide-gated channel, photoreceptor, Rod photoreceptor cGMP-gated channel subunit alpha) is encoded by the CNGA1 (also known as CNCG, CNCG1) gene (Gene ID: 281700) in bovine species. CNGA1 is a multi-pass membrane protein with four cytoplasmic domains, six transmembrane domains, and three extracellular domains. It is a subunit of the rod cyclic GMP-gated cation channel that is localized to the rod outer segment and is involved in the final stage of the phototransduction pathway. It forms a heterotetramer with CNGB1 (in a 3,1 ratio) but may also form homotetrameric channels that are strongly activated by saturating cGMP. When light hits rod photoreceptors, cGMP levels decrease that results in rapid closure of CNGA1/CNGB1 channels and hyperpolarization of the membrane potential. In this channel, CNGA1 forms a central channel gate in the middle of the membrane and occludes the central cavity. CNGA1 has two structural components: the membrane-spanning S1-S6 region and the cytosolic ligand gating apparatus. The transmembrane S1-S6 region of each subunit is separated into an S1-S4 voltage-sensor domain and an S5-S6 pore domain. The cytosolic soluble fragment of CNGA1 forms the gating apparatus in a channel tetramer that is responsible for cGMP activation of the channel. (Ref.: Xue, J., et al. (2021). Neuron. 109(8), 1302-1313, Cook, NJ., et al. (1989). J. Biol. Chem. 264(12), 6996-6999).