Forms a voltage-independent potassium channel activated by intracellular calcium (PubMed:11557517, PubMed:13679367, PubMed:14657188). Activation is followed by membrane hyperpolarization. Thought to regulate neuronal excitability by contributing to the slow component of synaptic afterhyperpolarization. Inhibited by bee venom neurotoxin apamin (PubMed:11557517, PubMed:13679367, PubMed:14657188). Inhibited by UCL 1684 and tetraethylammonium (TEA) (By similarity). Heterooligomer. The complex is composed of 4 channel subunits each of which binds to a calmodulin subunit which regulates the channel activity through calcium-binding (By similarity). Interacts (via N-terminal domain) with MPP2 (PubMed:26880549). Expressed in atrial and ventricular myocytes with higher levels in atrial myocytes (at protein level). Highly expressed in brain, liver and colon with low levels in kidney and testis. In colon, detected in smooth muscle cells. Belongs to the potassium channel KCNN family. KCa2.2/KCNN2 subfamily. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.