Forms a voltage-independent potassium channel that is activated by intracellular calcium (PubMed:9705284). Activation is followed by membrane hyperpolarization which promotes calcium influx. Required for maximal calcium influx and proliferation during the reactivation of naive T-cells (PubMed:20884616). Plays a role in the late stages of EGF-induced macropinocytosis (By similarity). The channel is inhibited by clotrimazole and charybdotoxin but is insensitive to apamin. Heterotetramer of potassium channel proteins (Probable). Interacts with MTMR6 (By similarity). Phosphorylation at His-356 by NDKB activates the channel, and conversely it's dephosphorylation by PHPT1 inhibits the channel. Belongs to the potassium channel KCNN family. KCa3.1/KCNN4 subfamily.