Acts as cyclic nucleotide-gated ion channel. Can be activated by cyclic AMP which leads to an opening of the cation channel. May be responsible for cAMP-induced calcium entry in cells and thus should be involved in the calcium signal transduction. Could transport K(+), Na(+) and Pb(2+). Homotetramer or heterotetramer (Potential). Binds calmodulin-2/3/5 with a higher affinity than calmodulin-1/4. Expressed in the whole plant but only weakly in roots. The binding of calmodulin to the C-terminus might interfere with cyclic nucleotide binding and thus channel activation. Plants exhibit an improved tolerance to Pb(2+). Belongs to the cyclic nucleotide-gated cation channel (TC 1.A.1.5) family.