Forms a voltage-independent potassium channel activated by intracellular calcium (PubMed:11557517). Activation is followed by membrane hyperpolarization (By similarity). Thought to regulate neuronal excitability by contributing to the slow component of synaptic afterhyperpolarization (By similarity). Inhibited by bee venom neurotoxin apamin. 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 with CALM1 (By similarity). Expressed at low levels in atrial and ventricular myocytes (at protein level). Belongs to the potassium channel KCNN family. KCa2.3/KCNN3 subfamily.