Pore-forming subunit of a voltage-gated ion channel. Permeable to monovalent cations, divalent cations and anions with selectivity Ca(2+) > Mg(2+) > Na(+) = K(+) > Cl(-). Acts both as a voltage-gated and calcium-activated ion channel. Required for normal locomotion. Expressed in head and body wall muscles, IL2, ASG, ASI, ASJ, PHA and PHB sensory neurons, and spermatheca. Uncoordinated locomotion with mutants showing reduced forward velocity, muscle force and power production. Belongs to the CALHM family.