The opening of the two pores of the Hv1 voltage-gated proton channel is tuned by cooperativity

Tombola, Francesco; Ulbrich, Maximilian H.; Kohout, Susy C.; Isacoff, Ehud Y.

doi:10.1038/nsmb.1738

Cited by 117 publications

(194 citation statements)

References 37 publications

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“…As a functional dimer, hHv1 shows strong cooperativity during activation gating, involving at least two conformational changes (10,48,49); in view of this, and considering the present data, we suggest that cooperativity in hHv1 dimer derives from three independent interactions: the presence of a covalent linkage at C249, interactions within the C-terminal coiled coil (37), and the ability of the VSDs to dimerize (Lower Left) Mutant 121C at top of S1 can form spontaneous disulfide linkage in native hHv1 (38). (Right) C β distances between hHv1 monomer according to the CiVSD-WT dimer (PDB ID code 4G80).…”

Section: Discussionmentioning

confidence: 99%

Resting state of the human proton channel dimer in a lipid bilayer

Shen

Treger

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

140

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The voltage-gated proton channel Hv1 plays a critical role in the fast proton translocation that underlies a wide range of physiological functions, including the phagocytic respiratory burst, sperm motility, apoptosis, and metastatic cancer. Both voltage activation and proton conduction are carried out by a voltage-sensing domain (VSD) with strong similarity to canonical VSDs in voltage-dependent cation channels and enzymes. We set out to determine the structural properties of membrane-reconstituted human proton channel (hHv1) in its resting conformation using electron paramagnetic resonance spectroscopy together with biochemical and computational methods. We evaluated existing structural templates and generated a spectroscopically constrained model of the hHv1 dimer based on the Ci-VSD structure at resting state. Mapped accessibility data revealed deep water penetration through hHv1, suggesting a highly focused electric field, comprising two turns of helix along the fourth transmembrane segment. This region likely contains the H + selectivity filter and the conduction pore. Our 3D model offers plausible explanations for existing electrophysiological and biochemical data, offering an explicit mechanism for voltage activation based on a one-click sliding helix conformational rearrangement.V oltage-gated proton channels (hHv1) represent a remarkable evolutionary adaptation of canonical voltage sensing domain (VSD). In hHv1, both voltage-sensing and ion (H + ) conduction are carried out by a single domain, and undergo a global conformational rearrangement (1, 2). In humans, hHv1 is widely expressed and required for a variety of physiological processes (3), including optimal reactive oxygen species production by NADPH oxidase (4-6), B-cell proliferation and differentiation (7), and regulation of human sperm motility (8). hHv1 folds as an antiparallel four-helix bundle with its fourth transmembrane segment (S4) containing three putative gating charges. Just as in the VSDs from ion channels and enzymes, the positively charged S4 moves outwardly in response to a depolarization (9). Beyond sensing the transmembrane voltage, S4 reorientation in hHv1 participates in the formation of a protonselective permeation pathway responsible for the generation of the proton currents that underlie its multiple physiological functions (10, 11).Despite high sequence similarity and a common structural blueprint, VSDs from ion channels and enzymes display a wide range of electrophysiological properties; these include large variations in effective gating charge (z = ∼0.9 to ∼3.6 e − ) and midpoints of activation (V 1/2 = ∼−150 to ∼+150 mV). Existing VSD crystal structures (12-16) have provided key data on the arrangement and orientation of the transmembrane helices S1-S4, while at the same time revealed a considerable structural heterogeneity-particularly, the number and positions of both the gating charges and their compensating countercharges in relation to the hydrophobic "plug" or "gasket" electrically separating the intra-and extrace...

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Section: Discussionmentioning

confidence: 99%

Resting state of the human proton channel dimer in a lipid bilayer

Shen

Treger

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

140

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“…It has been proposed that the gating movement of one monomeric channel subunit affects the gating of the other subunit within the dimeric unit [16][17][18] . We observed, in this study, dimerization by the coiledcoil assembly affected the thermosensitive gating.…”

Section: Coiled-coil Assembly Domain Of Mhv1/vsop and Its Structurementioning

confidence: 99%

“…One characteristic derived from the dimer assembly in the Hv channel is the cooperative channel gating-that is, the gating movement of one monomeric channel subunit affects the gating of the other subunit within the dimeric unit [16][17][18] . However, it remains unclear through which part of the channel the conformational change is transmitted from one subunit to the other during channel gating.…”

mentioning

confidence: 99%

The cytoplasmic coiled-coil mediates cooperative gating temperature sensitivity in the voltage-gated H+ channel Hv1

et al. 2012

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Hv1/VsoP is a dimeric voltage-gated H + channel in which the gating of one subunit is reportedly coupled to that of the other subunit within the dimer. The molecular basis for dimer formation and intersubunit coupling, however, remains unknown. Here we show that the carboxy terminus ends downstream of the s4 voltage-sensor helix twist in a dimer coiled-coil architecture, which mediates cooperative gating. We also show that the temperature-dependent activation of H + current through Hv1/VsoP is regulated by thermostability of the coiled-coil domain, and that this regulation is altered by mutation of the linker between s4 and the coiled-coil. Cooperative gating within the dimer is also dependent on the linker structure, which circular dichroism spectrum analysis suggests is α-helical. our results indicate that the cytoplasmic coiled-coil strands form continuous α-helices with s4 and mediate cooperative gating to adjust the range of temperatures over which Hv1/VsoP operates.

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“…Unlike other voltage-gated ion channels (VGICs), Hv1 is composed of two identical transmembrane (TM) subunits. Each monomer is formed mainly by a voltage-sensing domain (VSD) and is fully functional (8)(9)(10). Therefore, compared with other VGICs, Hv1 lacks the conventional pore domain ( Fig.…”

mentioning

confidence: 99%

On the role of water density fluctuations in the inhibition of a proton channel

Gianti

Delemotte

Klein

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Hv1 is a transmembrane four-helix bundle that transports protons in a voltage-controlled manner. Its crucial role in many pathological conditions, including cancer and ischemic brain damage, makes Hv1 a promising drug target. Starting from the recently solved crystal structure of Hv1, we used structural modeling and molecular dynamics simulations to characterize the channel's most relevant conformations along the activation cycle. We then performed computational docking of known Hv1 inhibitors, 2-guanidinobenzimidazole (2GBI) and analogs. Although salt-bridge patterns and electrostatic potential profiles are well-defined and distinctive features of activated versus nonactivated states, the water distribution along the channel lumen is dynamic and reflects a conformational heterogeneity inherent to each state. In fact, pore waters assemble into intermittent hydrogen-bonded clusters that are replaced by the inhibitor moieties upon ligand binding. The entropic gain resulting from releasing these conformationally restrained waters to the bulk solvent is likely a major contributor to the binding free energy. Accordingly, we mapped the water density fluctuations inside the pore of the channel and identified the regions of maximum fluctuation within putative binding sites. Two sites appear as outstanding: One is the already known binding pocket of 2GBI, which is accessible to ligands from the intracellular side; the other is a site located at the exit of the proton permeation pathway. Our analysis of the waters confined in the hydrophobic cavities of Hv1 suggests a general strategy for drug discovery that can be applied to any ion channel.Hv1 | drug design | pore waters | binding site discovery | confined waters

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The opening of the two pores of the Hv1 voltage-gated proton channel is tuned by cooperativity

Cited by 117 publications

References 37 publications

Resting state of the human proton channel dimer in a lipid bilayer

Resting state of the human proton channel dimer in a lipid bilayer

The cytoplasmic coiled-coil mediates cooperative gating temperature sensitivity in the voltage-gated H+ channel Hv1

On the role of water density fluctuations in the inhibition of a proton channel

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