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Does Proton Conduction in the Voltage-Gated H⁺ Channel hHv1 Involve Grotthuss-Like Hopping via Acidic Residues?

ABSTRACT: Hv1s are ubiquitous highly selective voltage-gated proton channels involved in male fertility, immunology, and the invasiveness of certain forms of breast cancer. The mechanism of proton extrusion in Hv1 is not yet understood, while it constitutes the first step toward the design of high-affinity drugs aimed at this important pharmacological target. In this contribution, we explore the details of the mechanism via an integrative approach, using classical and QM/MM molecular dynamics simulations of a monomeric hHv1 model. We propose that protons localize in three binding sites along the channel lumen, formed by three pairs of conserved negatively charged residues lining the pore: D174/E153, D112/D185, and E119/D123. Local rearrangements, involving notably a dihedral transition of F150, a conserved phenylalanine lining the permeation pathway, appear to allow protons to hop from one acidic residue to the next through a bridging water molecule. These results constitute a first attempt at rationalizing hHv1 selectivity for H⁺ and the role played by D112 in this process. They pave the way for further quantitative characterization of H⁺ transport in hHv1.

SUBMITTER: van Keulen SC

PROVIDER: S-EPMC6310143 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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Does Proton Conduction in the Voltage-Gated H<sup>+</sup> Channel hHv1 Involve Grotthuss-Like Hopping via Acidic Residues?

van Keulen Siri C SC Gianti Eleonora E Carnevale Vincenzo V Klein Michael L ML Rothlisberger Ursula U Delemotte Lucie L

The journal of physical chemistry. B 20161118 15

Hv1s are ubiquitous highly selective voltage-gated proton channels involved in male fertility, immunology, and the invasiveness of certain forms of breast cancer. The mechanism of proton extrusion in Hv1 is not yet understood, while it constitutes the first step toward the design of high-affinity drugs aimed at this important pharmacological target. In this contribution, we explore the details of the mechanism via an integrative approach, using classical and QM/MM molecular dynamics simulations ...[more]

PMID: 27801578

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Project description:Extraordinary selectivity is crucial to all proton-conducting molecules, including the human voltage-gated proton channel (hHV1), because the proton concentration is >10(6) times lower than that of other cations. Here we use "selectivity filter scanning" to elucidate the molecular requirements for proton-specific conduction in hHV1. Asp(112), in the middle of the S1 transmembrane helix, is an essential part of the selectivity filter in wild-type (WT) channels. After neutralizing Asp(112) by mutating it to Ala (D112A), we introduced Asp at each position along S1 from 108 to 118, searching for "second site suppressor" activity. Surprisingly, most mutants lacked even the anion conduction exhibited by D112A. Proton-specific conduction was restored only with Asp or Glu at position 116. The D112V/V116D channel strikingly resembled WT in selectivity, kinetics, and ΔpH-dependent gating. The S4 segment of this mutant has similar accessibility to WT in open channels, because R211H/D112V/V116D was inhibited by internally applied Zn(2+). Asp at position 109 allowed anion permeation in combination with D112A but did not rescue function in the nonconducting D112V mutant, indicating that selectivity is established externally to the constriction at F150. The three positions that permitted conduction all line the pore in our homology model, clearly delineating the conduction pathway. Evidently, a carboxyl group must face the pore directly to enable conduction. Molecular dynamics simulations indicate reorganization of hydrogen bond networks in the external vestibule in D112V/V116D. At both positions where it produces proton selectivity, Asp frequently engages in salt linkage with one or more Arg residues from S4. Surprisingly, mean hydration profiles were similar in proton-selective, anion-permeable, and nonconducting constructs. That the selectivity filter functions in a new location helps to define local environmental features required to produce proton-selective conduction.

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Does Proton Conduction in the Voltage-Gated H⁺ Channel hHv1 Involve Grotthuss-Like Hopping via Acidic Residues?

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Does Proton Conduction in the Voltage-Gated H<sup>+</sup> Channel hHv1 Involve Grotthuss-Like Hopping via Acidic Residues?

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Does Proton Conduction in the Voltage-Gated H+ Channel hHv1 Involve Grotthuss-Like Hopping via Acidic Residues?

Publications

Does Proton Conduction in the Voltage-Gated H<sup>+</sup> Channel hHv1 Involve Grotthuss-Like Hopping via Acidic Residues?

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Does Proton Conduction in the Voltage-Gated H⁺ Channel hHv1 Involve Grotthuss-Like Hopping via Acidic Residues?