Structure of the Shaker Kv channel and mechanism of slow C-type inactivation

Tan, Xiao-Feng; Bae, Chanhyung; Stix, Robyn; Fernández-Mariño, Ana I.; Huffer, Katherine E.; Chang, Tsun-Hsu; Jiang, Junchen; Faraldo‐Gómez, José D.; Swartz, Kenton J.

doi:10.1126/sciadv.abm7814

Cited by 82 publications

(86 citation statements)

References 98 publications

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“…Sodium conduction across the C-type inactivated state has been experimentally observed in hERG and also in the voltage-gated Shaker channel. 42 Furthermore, in recent experimental structures of a fast inactivating mutant of Shaker, both by cryo-EM 43 and by X-ray crystallography, 44 the SF appeared with binding sites S3 and S4 perfectly intact but with S1 and S2 sites enlarged compared to the canonical structure ( Figure 4 b). Thus, inactivation of Shaker seems to imply a widening of the extracellular portion of the SF rather than a constriction of its central region, as observed in the KcsA channel.…”

Section: Discussionmentioning

confidence: 88%

Early Steps in C-Type Inactivation of the hERG Potassium Channel

Pettini

Domene

Furini

2022

J. Chem. Inf. Model.

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Fast C-type inactivation confers distinctive functional properties to the hERG potassium channel, and its association to inherited and acquired cardiac arrythmias makes the study of the inactivation mechanism of hERG at the atomic detail of paramount importance. At present, two models have been proposed to describe C-type inactivation in K+-channels. Experimental data and computational work on the bacterial KcsA channel support the hypothesis that C-type inactivation results from a closure of the selectivity filter that sterically impedes ion conduction. Alternatively, recent experimental structures of a mutated Shaker channel revealed a widening of the extracellular portion of the selectivity filter, which might diminish conductance by interfering with the mechanism of ion permeation. Here, we performed molecular dynamics simulations of the wild-type hERG, a non-inactivating mutant (hERG-N629D), and a mutant that inactivates faster than the wild-type channel (hERG-F627Y) to find out which and if any of the two reported C-type inactivation mechanisms applies to hERG. Closure events of the selectivity filter were not observed in any of the simulated trajectories but instead, the extracellular section of the selectivity filter deviated from the canonical conductive structure of potassium channels. The degree of widening of the potassium binding sites at the extracellular entrance of the channel was directly related to the degree of inactivation with hERG-F627Y > wild-type hERG > hERG-N629D. These findings support the hypothesis that C-type inactivation in hERG entails a widening of the extracellular entrance of the channel rather than a closure of the selectivity filter.

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Section: Discussionmentioning

confidence: 88%

Early Steps in C-Type Inactivation of the hERG Potassium Channel

Pettini

Domene

Furini

2022

J. Chem. Inf. Model.

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“…High-resolution cryoEM and computer simulations have revealed additional dilated SF structures of the activated and C-type inactivated Shaker Kv channel and its W434 mutant in lipid bilayers 53 . A recent study reported structures of Kv1.3 channels that showed a dynamic selectivity filter with two discernable dilated conformations 54 , the authors hypothesizing that these may correspond to partially inactivated and inactivated states of the channel.…”

Section: Discussionmentioning

confidence: 99%

Conformational plasticity of NaK2K and TREK2 potassium channel selectivity filters

Matamoros

Brettmann

et al. 2023

Nat Commun

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The K+ channel selectivity filter (SF) is defined by TxGYG amino acid sequences that generate four identical K+ binding sites (S1-S4). Only two sites (S3, S4) are present in the non-selective bacterial NaK channel, but a four-site K+-selective SF is obtained by mutating the wild-type TVGDGN SF sequence to a canonical K+ channel TVGYGD sequence (NaK2K mutant). Using single molecule FRET (smFRET), we show that the SF of NaK2K, but not of non-selective NaK, is ion-dependent, with the constricted SF configuration stabilized in high K+ conditions. Patch-clamp electrophysiology and non-canonical fluorescent amino acid incorporation show that NaK2K selectivity is reduced by crosslinking to limit SF conformational movement. Finally, the eukaryotic K+ channel TREK2 SF exhibits essentially identical smFRET-reported ion-dependent conformations as in prokaryotic K+ channels. Our results establish the generality of K+-induced SF conformational stability across the K+ channel superfamily, and introduce an approach to study manipulation of channel selectivity.

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“…For example, the selectivity filter of the K + channel KcsA adopts conductive or collapsed conformations, depending on the concentration of K + ( 79 , 83 ). Ion selectivity filter conformational changes also underlie pH dependence and inactivation gating in certain K2P and Shaker potassium channels ( 84 , 85 ). The observations that the selectivity filter of MCU has the same conformation in all structures determined to date, including those with MICU1-MICU2 bound, suggest that the selectivity filter does not undergo large conformational changes.…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of ion selectivity and throughput in the mitochondrial calcium uniporter

Delgado

Long

2022

Sci. Adv.

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The mitochondrial calcium uniporter, which regulates aerobic metabolism by catalyzing mitochondrial Ca 2+ influx, is arguably the most selective ion channel known. The mechanisms for this exquisite Ca 2+ selectivity have not been defined. Here, using a reconstituted system, we study the electrical properties of the channel’s minimal Ca 2+ -conducting complex, MCU-EMRE, from Tribolium castaneum to probe ion selectivity mechanisms. The wild-type Tc MCU-EMRE complex recapitulates hallmark electrophysiological properties of endogenous Uniporter channels. Through interrogation of pore-lining mutants, we find that a ring of glutamate residues, the “E-locus,” serves as the channel’s selectivity filter. Unexpectedly, a nearby “D-locus” at the mouth of the pore has diminutive influence on selectivity. Anomalous mole fraction effects indicate that multiple Ca 2+ ions are accommodated within the E-locus. By facilitating ion-ion interactions, the E-locus engenders both exquisite Ca 2+ selectivity and high ion throughput. Direct comparison with structural information yields the basis for selective Ca 2+ conduction by the channel.

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Structure of the Shaker Kv channel and mechanism of slow C-type inactivation

Cited by 82 publications

References 98 publications

Early Steps in C-Type Inactivation of the hERG Potassium Channel

Early Steps in C-Type Inactivation of the hERG Potassium Channel

Conformational plasticity of NaK2K and TREK2 potassium channel selectivity filters

Mechanisms of ion selectivity and throughput in the mitochondrial calcium uniporter

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