Pore-forming subunit of a voltage-gated ion channel, also permeable to larger molecules including ATP (PubMed:29681531). Together with CALHM1, forms a fast-activating voltage-gated ATP-release channel in type II taste bud cells (TBCs) (PubMed:29681531). CALHM1-CALHM3-mediated ATP released acts as a neurotransmitter to gustatory neurons in response to GPCR-mediated tastes, including sweet, bitter and umami substances (PubMed:29681531). Associates with CALHM1 as a pore-forming subunit in an hetero-hexameric channel complex. Localizes to the basolateral membrane of epithelial cells including taste cells. Expressed in taste bud cells. Genetic deletion eliminates voltage-gated nonselective currents and taste-evoked ATP release in type II TBCs without affecting cell excitability or diminishing Calhm1 expression, and results in the loss of responses to sweet, umami and bitter tastes. Belongs to the CALHM family.