Pore dimensions and the role of occupancy in unitary conductance of Shaker K channels

Díaz-Franulic, Ignacio; Sepúlveda, Romina V.; Navarro-Quezada, Nieves; González-Nilo, Fernando D.; Naranjo, David

doi:10.1085/jgp.201411353

Cited by 27 publications

(56 citation statements)

References 46 publications

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“…Our osmotic results are in agreement with the overall VSR changes in solvent accessibility during Shaker and in other VSD proteins activation (7,10,39,40). The large water numbers that we found surpass arginine hydration numbers by 5-to 10-fold, being instead comparable with the volume of the channel's pore cavity, ∼1,600 Å 3 (41)(42)(43). Thus, our numbers probably represent conformational changes linked to the VSRs movement.…”

Section: Discussionsupporting

confidence: 88%

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Gating-induced large aqueous volumetric remodeling and aspartate tolerance in the voltage sensor domain of Shaker K ⁺ channels

Díaz-Franulic

González-Pérez

Moldenhauer

et al. 2018

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

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Neurons encode electrical signals with critically tuned voltage-gated ion channels and enzymes. Dedicated voltage sensor domains (VSDs) in these membrane proteins activate coordinately with an unresolved structural change. Such change conveys the transmembrane translocation of four positively charged arginine side chains, the voltage-sensing residues (VSRs; R1-R4). Countercharges and lipid phosphohead groups likely stabilize these VSRs within the low-dielectric core of the protein. However, the role of hydration, a sign-independent charge stabilizer, remains unclear. We replaced all VSRs and their neighboring residues with negatively charged aspartates in a voltage-gated potassium channel. The ensuing mild functional effects indicate that hydration is also important in VSR stabilization. The voltage dependency of the VSR aspartate variants approached the expected arithmetic summation of charges at VSR positions, as if negative and positive side chains faced similar pathways. In contrast, aspartates introduced between R2 and R3 did not affect voltage dependence as if the side chains moved outside the electric field or together with it, undergoing a large displacement and volumetric remodeling. Accordingly, VSR performed osmotic work at both internal and external aqueous interfaces. Individual VSR contributions to volumetric works approached arithmetical additivity but were largely dissimilar. While R1 and R4 displaced small volumes, R2 and R3 volumetric works were massive and vectorially opposed, favoring large aqueous remodeling during VSD activation. These diverse volumetric works are, at least for R2 and R3, not compatible with VSR translocation across a unique stationary charge transfer center. Instead, VSRs may follow separated pathways across a fluctuating low-dielectric septum.

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Section: Discussionsupporting

confidence: 88%

“…Site-Directed Mutagenesis, Channel Expression, and Electrophysiology. All Shaker mutant stems from Shaker B (Δ64-6) were generated as before (3,43).…”

Section: Methodsmentioning

confidence: 99%

Gating-induced large aqueous volumetric remodeling and aspartate tolerance in the voltage sensor domain of Shaker K ⁺ channels

Díaz-Franulic

González-Pérez

Moldenhauer

et al. 2018

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

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“…While all K channels exhibit specificity for K + ions over Na + ions, each K channel subfamily is unique in single channel properties(Naranjo et al, 2016), with conductance of the single channel being dependent on rate-limiting structures within the permeation path. Multiple studies of various K channel sub-types have converged to the same conclusion that negative charges lining the pore below the SF as well as steric dimensions (width and length) of the hydrophobic regions of the pore act as major determinants of single channel conductance, by varying K + ion accessibility to the SF(Brelidze et al, 2003; Diaz-Franulic et al, 2015; Naranjo et al, 2016; Nimigean et al, 2003). The Kir channel pore is uniquely long (~7 nm), due to the cytoplasmic extension (~ 4 nm) that is provided by the intracellular CTD(Naranjo et al, 2016), and also lined by several charged residues (3 acidic and 3 basic residues per subunit).…”

Section: Discussionmentioning

confidence: 95%

Atomistic basis of opening and conduction in mammalian inward rectifier potassium (Kir2.2) channels

Zangerl-Plessl

Lee

Maksaev

et al. 2019

Preprint

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18 simulations, single channel recordings. 19 20 21 22 Potassium ion conduction through open potassium channels is essential to 23 control of membrane potentials in all cells. To elucidate the open conformation 24 and hence the mechanism of K + ion conduction in the classical inward rectifier 25 Kir2.2, we introduced a negative charge (G178D) at the crossing point of the inner 26 helix bundle (HBC), the location of ligand-dependent gating. This 'forced open' 27 mutation generated channels that were active even in the complete absence of 28 phosphoinositol-4,5-bisphosphate (PIP 2 ), an otherwise essential ligand for Kir 29 channel opening. Crystal structures were obtained at a resolution of 3.6 Å without 30 PIP 2 bound, or 2.8 Å in complex with PIP 2 . The latter revealed a slight widening at 31 the HBC, through backbone movement. Molecular dynamics (MD) simulations 32 showed that subsequent spontaneous wetting of the pore through the HBC gate 33 region allowed K + ion movement across the HBC and conduction through the 34 channel. Further simulations reveal atomistic details of the opening process and 35 highlight the role of pore lining acidic residues in K + conduction through Kir2 36 channels.

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“…The number of ions in the pore While all K channels exhibit specificity for K + ions over Na + ions, each K channel subfamily is unique in single-channel properties (Naranjo et al, 2016), with conductance of the single channel being dependent on rate-limiting structures within the permeation path. Multiple studies of various K channel subtypes have converged to the same conclusion that negative charges lining the pore below the SF as well as steric dimensions (width and length) of the hydrophobic regions of the pore act as major determinants of single-channel conductance, by varying K + ion accessibility to the SF (Brelidze et al, 2003;Díaz-Franulic et al, 2015;Naranjo et al, 2016;Nimigean et al, 2003). The Kir channel pore is uniquely long (∼7 nm), due to the cytoplasmic extension (∼4 nm) that is provided by the intracellular CTD (Naranjo et al, 2016) and also lined by several charged residues (three acidic and three basic residues per subunit).…”

Section: Discussionmentioning

confidence: 96%

Atomistic basis of opening and conduction in mammalian inward rectifier potassium (Kir2.2) channels

et al. 2019

View full text Add to dashboard Cite

Potassium ion conduction through open potassium channels is essential to control of membrane potentials in all cells. To elucidate the open conformation and hence the mechanism of K+ ion conduction in the classic inward rectifier Kir2.2, we introduced a negative charge (G178D) at the crossing point of the inner helix bundle, the location of ligand-dependent gating. This “forced open” mutation generated channels that were active even in the complete absence of phosphatidylinositol-4,5-bisphosphate (PIP2), an otherwise essential ligand for Kir channel opening. Crystal structures were obtained at a resolution of 3.6 Å without PIP2 bound, or 2.8 Å in complex with PIP2. The latter revealed a slight widening at the helix bundle crossing (HBC) through backbone movement. MD simulations showed that subsequent spontaneous wetting of the pore through the HBC gate region allowed K+ ion movement across the HBC and conduction through the channel. Further simulations reveal atomistic details of the opening process and highlight the role of pore-lining acidic residues in K+ conduction through Kir2 channels.

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Pore dimensions and the role of occupancy in unitary conductance of Shaker K channels

Abstract: The resistance of the inner vestibule limits Shaker’s conductance.

Cited by 27 publications

References 46 publications

Gating-induced large aqueous volumetric remodeling and aspartate tolerance in the voltage sensor domain of Shaker K ⁺ channels

Gating-induced large aqueous volumetric remodeling and aspartate tolerance in the voltage sensor domain of Shaker K ⁺ channels

Atomistic basis of opening and conduction in mammalian inward rectifier potassium (Kir2.2) channels

Atomistic basis of opening and conduction in mammalian inward rectifier potassium (Kir2.2) channels

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Pore dimensions and the role of occupancy in unitary conductance of Shaker K channels

Abstract: The resistance of the inner vestibule limits Shaker’s conductance.

Cited by 27 publications

References 46 publications

Gating-induced large aqueous volumetric remodeling and aspartate tolerance in the voltage sensor domain of Shaker K + channels

Gating-induced large aqueous volumetric remodeling and aspartate tolerance in the voltage sensor domain of Shaker K + channels

Atomistic basis of opening and conduction in mammalian inward rectifier potassium (Kir2.2) channels

Atomistic basis of opening and conduction in mammalian inward rectifier potassium (Kir2.2) channels

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Gating-induced large aqueous volumetric remodeling and aspartate tolerance in the voltage sensor domain of Shaker K ⁺ channels

Gating-induced large aqueous volumetric remodeling and aspartate tolerance in the voltage sensor domain of Shaker K ⁺ channels