CALMODULIN REGULATION OF CYCLIC-NUCLEOTIDE-GATED CHANNELS

Cyclic-nucleotide-gated (CNG) channels play key roles in photoreceptor and olfactory signal-transduction pathways. Recent studies have focus ed on the molecular characterization of CNG channel subunits and on th e identification of the structural domains that contribute to ligand s electivity and affinity, ion gating and permeation, and regulation of channel activity, Calmodulin has been shown to bind directly to the ro d and olfactory channels and to modulate their sensitivity to cyclic n ucleotides, This Ca2+-dependent regulation of channel activity appears to play a role in the termination of the signal-transduction pathway in olfactory neurons and rod photoreceptor cells. It remains to be det ermined whether calmodulin also regulates the activity of related chan nels in other cells.