Enables cGMP binding activity; intracellular cGMP-activated cation channel activity; and protein C-terminus binding activity. Involved in several processes, including inorganic cation import across plasma membrane; response to cAMP; and response to magnesium ion. Located in several cellular components, including axon initial segment; glial cell projection; and perikaryon. Human ortholog(s) of this gene implicated in achromatopsia 2 and color blindness. Orthologous to human CNGA3 (cyclic nucleotide gated channel subunit alpha 3). [provided by Alliance of Genome Resources, Apr 2022]