New 'kids' on the voltage-gated proton channel block.

So far one gene for Hv1 has been detected in studied species. The work presented by Chaves et al. in The FEBS Journal reported an 'Unexpected expansion of the voltage-gated proton channel family'. They searched for proton channel candidates and found three sequences in the genome of Aplysia californica (Ac), which were named AcHv1, AcHv2 and AcHv3. Based on electrophysiological experiments, AcHv1 and AcHv2 are voltage-gated channels. While AcHv1 behaves like Hv1 in other species, that is, it is voltage and pH-dependent, it can be inhibited by zinc and conducts protons outwardly, AcHv2 conducts protons inwards at symmetrical pH. AcHv3 constantly leaks protons, and its C-terminal part contains several cytoplasmic retention motifs. Through carefully designed and carried out electrophysiological experiments, Chaves et al. determined the biophysical parameters of all three proton channels, such as the voltage and the pH dependence, the threshold-voltage, the gating charge and the time constants of activation and inactivation. Comment on: https://doi.org/10.1111/febs.16617.