C-terminus-independent multimerization of Hv1 proton channels

The voltage-gated proton channel Hv1, assembles as a dimer when expressed in heterologous systems, likely reflecting its stoichiometry in native membranes. It is known that the dimeric interaction is mediated at least by specific transmembrane domain amino acid interactions and a coiled-coil interaction mediated by the intracellular C-terminus helices. Deletion of this last interaction (ΔC) has been thought to lead to disruption of dimers and production of monomeric channels, which remain functional as proton channels, albeit with different biophysical properties. Here, we present evidence that apart from activation kinetics, other biophysical properties of the ΔC channels are different to those of the WT, dimeric channels, and that the ΔC channels are still capable of efficiently forming dimers and maybe even reaching higher stoichiometry. Our results suggest that the C-terminal mediated interactions might help to ensure formation of dimers in full-length channels but are not necessary for their assembly.