Pore-forming subunit of an ATP-permeable channel (By similarity). In response to pathogen-derived and proinflammatory stimuli, relocates from intracellular compartments to NK-dendritic cell and NK-macrophage immune synapses where it mediates ATP efflux and NK cell activation involved in antimicrobial and antitumor responses (By similarity). May assemble to form gap junction channel-like structures with gating and ion conductance likely regulated by membrane lipids and voltage rather than by extracellular calcium levels (PubMed:32374262). . This is the function of CALHM6 (calcium homeostasis modulator family member 6, ENSG00000188820).