Visual signal transduction is mediated by a G-protein coupled cascade using cGMP as second messenger. This protein can be activated by cyclic GMP which leads to an opening of the cation channel and thereby causing a depolarization of cone photoreceptors. Essential for the generation of light-evoked electrical responses in the red-, green- and blue sensitive cones Induced a flickering channel gating, weakened the outward rectification in the presence of extracellular calcium, increased sensitivity for L-cis diltiazem and enhanced the cAMP efficacy of the channel when coexpressed with CNGB3 (By similarity). Could be responsible for cGMP-induced calcium entry in cells other than sensory cells. Might be involved in chemotaxis of sperm. Tetramer formed of three CNGA3 and one CNGB3 modulatory subunits (By similarity). Forms functional heterooligomeric channels with CNG4 in vitro. Testis, kidney, retinal cone and heart. The C-terminal coiled-coil domain mediates homotrimerization of CNGA subunits. Belongs to the cyclic nucleotide-gated cation channel (TC 1.A.1.5) family. CNGA3 subfamily.