Two B or not two B? Questioning the rotational symmetry of tetrameric ion channels.

Members of the voltage-gated family of ion channels generally demonstrate rotational symmetry about their pore regions. Recent evidence suggests that a subset of this family, the cyclic nucleotide-gated channels, may deviate from this pattern of rotational symmetry by having 3A:1B subunit stoichiometry. This finding raises many questions about the function, assembly, and trafficking of these and related ion channels and about the functional nonequivalence of subunits with identical amino acid sequences.