cGMP:CNG transports Na+ and Ca2+ into the rod outer segment

Stable Identifier
Reaction [transition]
Homo sapiens
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The cGMP-gated (CNG) channels are heterotetramers of three alpha subunits (CNGA1) and one beta subunit (CNGB1). Although the subunits bear structural similarities to voltage-gated potassium channels, the rod channel is only weakly voltage sensitive (Chen et al. 1993). Opening occurs with cGMP bound and rarely occurs in the absence of cGMP (hence the closed state is designated as CNG channel and the open status is designated as cGMP:CNG channel). In darkness, cGMP concentration is relatively high and cGMP-gated cation (CNG) channels are open to allow the influx of cations into the rod outer segment. The inward current is composed mainly of Na+ ions, with lesser contributions from Ca2+ ions and Mg2+ ions (Dhallan et al. 1992). The channel is outwardly rectifying so that over physiological membrane potentials, the inward current is proportional to the number of channels open and is nearly independent of voltage. Mutations in the CNG channel subunits can cause a recessive form of retinitis pigmentosa (
Literature References
PubMed ID Title Journal Year
12432397 The heteromeric cyclic nucleotide-gated channel adopts a 3A:1B stoichiometry

Yau, KW, Zhong, H, Molday, LL, Molday, RS

Nature 2002
16460277 CNG and HCN channels: two peas, one pod

Zagotta, WN, Craven, KB

Annu. Rev. Physiol. 2006
12467591 Subunit stoichiometry of the CNG channel of rod photoreceptors.

Ficek, N, Bauer, PJ, Weitz, D, Kremmer, E, Kaupp, UB

Neuron 2002
1379636 Human rod photoreceptor cGMP-gated channel: amino acid sequence, gene structure, and functional expression.

Reed, RR, Yau, KW, Nathans, J, Macke, JP, Dhallan, RS, Shows, TB

J Neurosci 1992
12467592 Rod cyclic nucleotide-gated channels have a stoichiometry of three CNGA1 subunits and one CNGB1 subunit.

Zheng, J, Zagotta, WN, Trudeau, MC

Neuron 2002
2578616 Induction by cyclic GMP of cationic conductance in plasma membrane of retinal rod outer segment

Kolesnikov, SS, Fesenko, EE, Lyubarsky, AL

Nature 1985
2457685 Calcium and magnesium fluxes across the plasma membrane of the toad rod outer segment

Yau, KW, Nakatani, K

J. Physiol. (Lond.) 1988
7682292 A new subunit of the cyclic nucleotide-gated cation channel in retinal rods

Peng, YW, Reed, RR, Yau, KW, Dhallan, RS, Ahamed, B, Chen, TY

Nature 1993
2422346 Electrical properties of the light-sensitive conductance of rods of the salamander Ambystoma tigrinum

Nunn, BJ, Baylor, DA

J. Physiol. (Lond.) 1986
Catalyst Activity

intracellular cyclic nucleotide activated cation channel activity of cGMP:CNG channel [plasma membrane]

Orthologous Events
Cross References
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