Unitary conductance of the voltage-sensitive proton channel HV1

Description

The voltage-sensitive proton selective channel HV1 is ubiquitously present in mammalian tissues. An aqueous pore provides the proton pathway. Intervening amino acid side chains render the channel impermeable to water [1]. Based on the hydrogen bonds formed between the permeating water molecules and the channel wall, HV1 would otherwise exhibit a water conductance comparable to aquaporins [2, 3]. The proton wire involves Grotthusslike proton hopping on top of intraluminal water molecules and titratable amino acids. Other proton-selective molecules engaged in bioenergetics possess a similar proton-conducting mechanism. Conceivably, HV1 exploits one or more of the arginines from the voltage sensor as part of the proton wire. Yet, proton release from arginines is slow, provided the side chain pKa in the channel lumen remains at the bulk level. It may limit the proton transport rate to roughly 10 protons per second. Here we tested the hypothesis by reconstituting the purified proton channel into lipid vesicles. We used pHluorin to tag the channel and measure intravesicular pH. Fluorescence correlation spectroscopy served to measure channel density [4]. Accounting for the number of channels per vesicle allows extracting the unitary channel conductance. The latter confirms the role of amino acids in proton transfer. We thank the European Union’s Horizon 2020 research and innovation program (Marie Skłodowska-Curie grant agreement No. 860592).

Period	22 Aug 2022
Event title	unbekannt/unknown
Event type	Conference
Location	FranceShow on map