 These activation and inactivation mechanisms both involve Ca2+ binding to calmodulin (CaM) in the IQ domain in the C-terminal tail of these channels.Cav1.2 channels are arranged in cluster of eight, on average, in the cell membrane.When calcium ions bind to calmodulin, which in turn binds to a Cav1.2 channel, it allows the Cav1.2 channels within a cluster to interact with each other.