K+ conduction and Mg2+ blockade in a Shaker Kv-channel single point mutant with an unusually high conductance

Cristian Moscoso, Ariela Vergara-Jaque, Valeria Márquez-Miranda, Romina V. Sepúlveda, Ignacio Valencia, Ignacio Díaz-Franulic, Fernando González-Nilo, David Naranjo

Resultado de la investigación: Article

6 Citas (Scopus)

Resumen

Potassium channels exhibit a large diversity of single-channel conductances. Shaker is a low-conductance K-channel in which Pro475→Asp, a single-point mutation near the internal pore entrance, promotes 6- to 8-fold higher unitary current. To assess the mechanism for this higher conductance, we measured Shaker-P475D single-channel current in a wide range of symmetrical K+ concentrations and voltages. Below 300 mM K+, the current-to-voltage relations (i-V) showed inward rectification that disappeared at 1000 mM K+. Single-channel conductance reached a maximum of ∼190 pS at saturating [K+], a value 4- to 5-fold larger than that estimated for the native channel. Intracellular Mg2+ blocked this variant with ∼100-fold higher affinity. Near zero voltage, blockade was competitively antagonized by K+; however, at voltages >100 mV, it was enhanced by K+. This result is consistent with a lock-in effect in a single-file diffusion regime of Mg2+ and K+ along the pore. Molecular-dynamics simulations revealed higher K+ density in the pore, especially near the Asp-475 side chains, as in the high-conductance MthK bacterial channel. The molecular dynamics also showed that K+ ions bound distally can coexist with other K+ or Mg2+ in the cavity, supporting a lock-in mechanism. The maximal K+ transport rate and higher occupancy could be due to a decrease in the electrostatic energy profile for K+ throughout the pore, reducing the energy wells and barriers differentially by ∼0.7 and ∼2 kT, respectively.

Idioma originalEnglish
Páginas (desde-hasta)1198-1207
Número de páginas10
PublicaciónBiophysical Journal
Volumen103
N.º6
DOI
EstadoPublished - 19 sep 2012

Huella dactilar

Molecular Dynamics Simulation
Potassium Channels
Static Electricity
Point Mutation
Ions

ASJC Scopus subject areas

  • Biophysics

Citar esto

Moscoso, C., Vergara-Jaque, A., Márquez-Miranda, V., Sepúlveda, R. V., Valencia, I., Díaz-Franulic, I., ... Naranjo, D. (2012). K+ conduction and Mg2+ blockade in a Shaker Kv-channel single point mutant with an unusually high conductance. Biophysical Journal, 103(6), 1198-1207. https://doi.org/10.1016/j.bpj.2012.08.015
Moscoso, Cristian ; Vergara-Jaque, Ariela ; Márquez-Miranda, Valeria ; Sepúlveda, Romina V. ; Valencia, Ignacio ; Díaz-Franulic, Ignacio ; González-Nilo, Fernando ; Naranjo, David. / K+ conduction and Mg2+ blockade in a Shaker Kv-channel single point mutant with an unusually high conductance. En: Biophysical Journal. 2012 ; Vol. 103, N.º 6. pp. 1198-1207.
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abstract = "Potassium channels exhibit a large diversity of single-channel conductances. Shaker is a low-conductance K-channel in which Pro475→Asp, a single-point mutation near the internal pore entrance, promotes 6- to 8-fold higher unitary current. To assess the mechanism for this higher conductance, we measured Shaker-P475D single-channel current in a wide range of symmetrical K+ concentrations and voltages. Below 300 mM K+, the current-to-voltage relations (i-V) showed inward rectification that disappeared at 1000 mM K+. Single-channel conductance reached a maximum of ∼190 pS at saturating [K+], a value 4- to 5-fold larger than that estimated for the native channel. Intracellular Mg2+ blocked this variant with ∼100-fold higher affinity. Near zero voltage, blockade was competitively antagonized by K+; however, at voltages >100 mV, it was enhanced by K+. This result is consistent with a lock-in effect in a single-file diffusion regime of Mg2+ and K+ along the pore. Molecular-dynamics simulations revealed higher K+ density in the pore, especially near the Asp-475 side chains, as in the high-conductance MthK bacterial channel. The molecular dynamics also showed that K+ ions bound distally can coexist with other K+ or Mg2+ in the cavity, supporting a lock-in mechanism. The maximal K+ transport rate and higher occupancy could be due to a decrease in the electrostatic energy profile for K+ throughout the pore, reducing the energy wells and barriers differentially by ∼0.7 and ∼2 kT, respectively.",
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Moscoso, C, Vergara-Jaque, A, Márquez-Miranda, V, Sepúlveda, RV, Valencia, I, Díaz-Franulic, I, González-Nilo, F & Naranjo, D 2012, 'K+ conduction and Mg2+ blockade in a Shaker Kv-channel single point mutant with an unusually high conductance', Biophysical Journal, vol. 103, n.º 6, pp. 1198-1207. https://doi.org/10.1016/j.bpj.2012.08.015

K+ conduction and Mg2+ blockade in a Shaker Kv-channel single point mutant with an unusually high conductance. / Moscoso, Cristian; Vergara-Jaque, Ariela; Márquez-Miranda, Valeria; Sepúlveda, Romina V.; Valencia, Ignacio; Díaz-Franulic, Ignacio; González-Nilo, Fernando; Naranjo, David.

En: Biophysical Journal, Vol. 103, N.º 6, 19.09.2012, p. 1198-1207.

Resultado de la investigación: Article

TY - JOUR

T1 - K+ conduction and Mg2+ blockade in a Shaker Kv-channel single point mutant with an unusually high conductance

AU - Moscoso, Cristian

AU - Vergara-Jaque, Ariela

AU - Márquez-Miranda, Valeria

AU - Sepúlveda, Romina V.

AU - Valencia, Ignacio

AU - Díaz-Franulic, Ignacio

AU - González-Nilo, Fernando

AU - Naranjo, David

PY - 2012/9/19

Y1 - 2012/9/19

N2 - Potassium channels exhibit a large diversity of single-channel conductances. Shaker is a low-conductance K-channel in which Pro475→Asp, a single-point mutation near the internal pore entrance, promotes 6- to 8-fold higher unitary current. To assess the mechanism for this higher conductance, we measured Shaker-P475D single-channel current in a wide range of symmetrical K+ concentrations and voltages. Below 300 mM K+, the current-to-voltage relations (i-V) showed inward rectification that disappeared at 1000 mM K+. Single-channel conductance reached a maximum of ∼190 pS at saturating [K+], a value 4- to 5-fold larger than that estimated for the native channel. Intracellular Mg2+ blocked this variant with ∼100-fold higher affinity. Near zero voltage, blockade was competitively antagonized by K+; however, at voltages >100 mV, it was enhanced by K+. This result is consistent with a lock-in effect in a single-file diffusion regime of Mg2+ and K+ along the pore. Molecular-dynamics simulations revealed higher K+ density in the pore, especially near the Asp-475 side chains, as in the high-conductance MthK bacterial channel. The molecular dynamics also showed that K+ ions bound distally can coexist with other K+ or Mg2+ in the cavity, supporting a lock-in mechanism. The maximal K+ transport rate and higher occupancy could be due to a decrease in the electrostatic energy profile for K+ throughout the pore, reducing the energy wells and barriers differentially by ∼0.7 and ∼2 kT, respectively.

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Moscoso C, Vergara-Jaque A, Márquez-Miranda V, Sepúlveda RV, Valencia I, Díaz-Franulic I y otros. K+ conduction and Mg2+ blockade in a Shaker Kv-channel single point mutant with an unusually high conductance. Biophysical Journal. 2012 sep 19;103(6):1198-1207. https://doi.org/10.1016/j.bpj.2012.08.015