Pore-forming subunit of a voltage-gated ion channel, also permeable to larger molecules including ATP. Together with CALHM1, forms a fast-activating voltage-gated ATP-release channel in type II taste bud cells (TBCs). CALHM1-CALHM3-mediated ATP released acts as a neurotransmitter to gustatory neurons in response to GPCR-mediated tastes, including sweet, bitter and umami substances. Associates with CALHM1 as a pore-forming subunit in an hetero-hexameric channel complex. Specifically expressed in circumvallate taste bud cells. Belongs to the CALHM family.