Conformational Changes and Gating at the Selectivity Filter of Potassium Channels

2008 ◽  
Vol 130 (29) ◽  
pp. 9474-9480 ◽  
Author(s):  
Carmen Domene ◽  
Michael L. Klein ◽  
Davide Branduardi ◽  
Francesco L. Gervasio ◽  
Michele Parrinello
Keyword(s):  
Potassium Channels ◽  
Conformational Changes ◽  
Selectivity Filter

scholarly journals K2P channel C-type gating involves asymmetric selectivity filter order-disorder transitions

2020 ◽  
Vol 6 (44) ◽  
pp. eabc9174
Author(s):  
Marco Lolicato ◽  
Andrew M. Natale ◽  
Fayal Abderemane-Ali ◽  
David Crottès ◽  
Sara Capponi ◽  
...  
Keyword(s):  
Potassium Channels ◽  
Conformational Changes ◽  
Structural Changes ◽  
Selectivity Filter ◽  
Anomalous Scattering ◽  
X Ray Crystallography ◽  
Gating Mechanisms ◽  
Cellular Excitability ◽  
Ion Binding Sites ◽  
Channel Modulator

K2P potassium channels regulate cellular excitability using their selectivity filter (C-type) gate. C-type gating mechanisms, best characterized in homotetrameric potassium channels, remain controversial and are attributed to selectivity filter pinching, dilation, or subtle structural changes. The extent to which such mechanisms control C-type gating of innately heterodimeric K2Ps is unknown. Here, combining K2P2.1 (TREK-1) x-ray crystallography in different potassium concentrations, potassium anomalous scattering, molecular dynamics, and electrophysiology, we uncover unprecedented, asymmetric, potassium-dependent conformational changes that underlie K2P C-type gating. These asymmetric order-disorder transitions, enabled by the K2P heterodimeric architecture, encompass pinching and dilation, disrupt the S1 and S2 ion binding sites, require the uniquely long K2P SF2-M4 loop and conserved “M3 glutamate network,” and are suppressed by the K2P C-type gate activator ML335. These findings demonstrate that two distinct C-type gating mechanisms can operate in one channel and underscore the SF2-M4 loop as a target for K2P channel modulator development.

scholarly journals Probing the Cavity of the Slow Inactivated Conformation of Shaker Potassium Channels

2007 ◽  
Vol 129 (5) ◽  
pp. 403-418 ◽  
Author(s):  
Gyorgy Panyi ◽  
Carol Deutsch
Keyword(s):  
Potassium Channels ◽  
Binding Site ◽  
Conformational Change ◽  
Marked Decrease ◽  
Selectivity Filter ◽  
Slow Inactivation ◽  
Voltage Gated ◽  
Activation Gate ◽  
Shaker Potassium Channels

Slow inactivation involves a local rearrangement of the outer mouth of voltage-gated potassium channels, but nothing is known regarding rearrangements in the cavity between the activation gate and the selectivity filter. We now report that the cavity undergoes a conformational change in the slow-inactivated state. This change is manifest as altered accessibility of residues facing the aqueous cavity and as a marked decrease in the affinity of tetraethylammonium for its internal binding site. These findings have implications for global alterations of the channel during slow inactivation and putative coupling between activation and slow-inactivation gates.

scholarly journals Structural Basis for pH-Gating of the K+ Channel TWIK1 at the Selectivity Filter

2021 ◽  
Author(s):  
Toby S Turney ◽  
Vivian Li ◽  
Stephen G Brohawn
Keyword(s):  
Conformational Changes ◽  
Pancreatic Beta Cells ◽  
Low Ph ◽  
Selectivity Filter ◽  
Structural Basis ◽  
K Channel ◽  
Open Conformation ◽  
Gating Mechanism ◽  
Lipid Nanodiscs ◽  
Pore Domain

TWIK1 is a widely expressed pH-gated two-pore domain K+ channel (K2P) that contributes to cardiac rhythm generation and insulin release from pancreatic beta cells. TWIK1 displays unique properties among K2Ps including low basal activity and inhibition by extracellular protons through incompletely understood mechanisms. Here, we present cryo-EM structures of TWIK1 in lipid nanodiscs at high and low pH that reveal a novel gating mechanism at the K+ selectivity filter. At high pH, TWIK1 adopts an open conformation. At low pH, protonation of an extracellular histidine results in a cascade of conformational changes that close the channel by sealing the top of the selectivity filter, displacing the helical cap to block extracellular ion access pathways, and opening gaps for lipid block of the intracellular cavity. These data provide a mechanistic understanding for extracellular pH-gating of TWIK1 and show how diverse mechanisms have evolved to gate the selectivity filter of K+ channels.

scholarly journals The conduction pathway of potassium channels is water free under physiological conditions

2019 ◽  
Vol 5 (7) ◽  
pp. eaaw6756 ◽  
Author(s):  
Carl Öster ◽  
Kitty Hendriks ◽  
Wojciech Kopec ◽  
Veniamin Chevelkov ◽  
Chaowei Shi ◽  
...  
Keyword(s):  
Potassium Channels ◽  
Direct Contact ◽  
Selectivity Filter ◽  
Water Molecules ◽  
Potassium Ions ◽  
Ion Conduction ◽  
Physiological Conditions ◽  
Conduction Pathway ◽  
Fundamental Process ◽  
Dynamics Simulations

Ion conduction through potassium channels is a fundamental process of life. On the basis of crystallographic data, it was originally proposed that potassium ions and water molecules are transported through the selectivity filter in an alternating arrangement, suggesting a “water-mediated” knock-on mechanism. Later on, this view was challenged by results from molecular dynamics simulations that revealed a “direct” knock-on mechanism where ions are in direct contact. Using solid-state nuclear magnetic resonance techniques tailored to characterize the interaction between water molecules and the ion channel, we show here that the selectivity filter of a potassium channel is free of water under physiological conditions. Our results are fully consistent with the direct knock-on mechanism of ion conduction but contradict the previously proposed water-mediated knock-on mechanism.

scholarly journals Conformational Changes in the Pore of CLC-0

2003 ◽  
Vol 122 (3) ◽  
pp. 277-294 ◽  
Author(s):  
Alessio Accardi ◽  
Michael Pusch
Keyword(s):  
Conformational Changes ◽  
Single Channel ◽  
General Structure ◽  
Point Mutations ◽  
Clofibric Acid ◽  
Selectivity Filter ◽  
Side Chain ◽  
Closed State ◽  
State Dependent ◽  
Channel Opening

The Torpedo Cl− channel, CLC-0, is inhibited by clofibric acid derivatives from the intracellular side. We used the slow gate-deficient mutant CLC-0C212S to investigate the mechanism of block by the clofibric acid–derivative p-chlorophenoxy-acetic acid (CPA). CPA blocks open channels with low affinity (KDO= 45 mM at 0 mV) and shows fast dissociation (koff = 490 s−1 at −140 mV). In contrast, the blocker binds to closed channels with higher affinity and with much slower kinetics. This state-dependent block coupled with the voltage dependence of the gating transitions results in a highly voltage-dependent inhibition of macroscopic currents (KD ∼1 mM at −140 mV; KD ∼65 mM at 60 mV). The large difference in CPA affinity of the open and closed state suggests that channel opening involves more than just a local conformational rearrangement. On the other hand, in a recent work (Dutzler, R., E.B. Campbell, and R. MacKinnon. 2003. Science. 300:108–112) it was proposed that the conformational change underlying channel opening is limited to a movement of a single side chain. A prediction of this latter model is that mutations that influence CPA binding to the channel should affect the affinities for an open and closed channel in a similar manner since the general structure of the pore remains largely unchanged. To test this hypothesis we introduced point mutations in four residues (S123, T471, Y512, and K519) that lie close to the intracellular pore mouth or to the putative selectivity filter. Mutation T471S alters CPA binding exclusively to closed channels. Pronounced effects on the open channel block are observed in three other mutants, S123T, Y512A, and K519Q. Together, these results collectively suggest that the structure of the CPA binding site is different in the open and closed state. Finally, replacement of Tyr 512, a residue directly coordinating the central Cl− ion in the crystal structure, with Phe or Ala has very little effect on single channel conductance and selectivity. These observations suggest that channel opening in CLC-0 consists in more than a movement of a side chain and that other parts of the channel and of the selectivity filter are probably involved.

scholarly journals Interfacial gating triad is crucial for electromechanical transduction in voltage-activated potassium channels

2014 ◽  
Vol 144 (5) ◽  
pp. 457-467 ◽  
Author(s):  
Sandipan Chowdhury ◽  
Benjamin M. Haehnel ◽  
Baron Chanda
Keyword(s):  
Potassium Channels ◽  
Conformational Changes ◽  
Electromechanical Coupling ◽  
Structural Integrity ◽  
Voltage Sensor ◽  
Amino Acid Residues ◽  
Kv Channel ◽  
Electromechanical Transduction ◽  
Voltage Dependent ◽  
Graph Theoretical Approach

Voltage-dependent potassium channels play a crucial role in electrical excitability and cellular signaling by regulating potassium ion flux across membranes. Movement of charged residues in the voltage-sensing domain leads to a series of conformational changes that culminate in channel opening in response to changes in membrane potential. However, the molecular machinery that relays these conformational changes from voltage sensor to the pore is not well understood. Here we use generalized interaction-energy analysis (GIA) to estimate the strength of site-specific interactions between amino acid residues putatively involved in the electromechanical coupling of the voltage sensor and pore in the outwardly rectifying KV channel. We identified candidate interactors at the interface between the S4–S5 linker and the pore domain using a structure-guided graph theoretical approach that revealed clusters of conserved and closely packed residues. One such cluster, located at the intracellular intersubunit interface, comprises three residues (arginine 394, glutamate 395, and tyrosine 485) that interact with each other. The calculated interaction energies were 3–5 kcal, which is especially notable given that the net free-energy change during activation of the Shaker KV channel is ∼14 kcal. We find that this triad is delicately maintained by balance of interactions that are responsible for structural integrity of the intersubunit interface while maintaining sufficient flexibility at a critical gating hinge for optimal transmission of force to the pore gate.

scholarly journals Gating modules of the AMPA receptor pore domain revealed by unnatural amino acid mutagenesis

2019 ◽  
Vol 116 (27) ◽  
pp. 13358-13367 ◽  
Author(s):  
Mette H. Poulsen ◽  
Anahita Poshtiban ◽  
Viktoria Klippenstein ◽  
Valentina Ghisi ◽  
Andrew J. R. Plested
Keyword(s):  
Amino Acid ◽  
Conformational Changes ◽  
Transmembrane Domain ◽  
Uv Light ◽  
Unnatural Amino Acid ◽  
Selectivity Filter ◽  
Unnatural Amino Acid Mutagenesis ◽  
Amino Acid Mutagenesis ◽  
Mutant Receptors ◽  
Pore Domain

Ionotropic glutamate receptors (iGluRs) are responsible for fast synaptic transmission throughout the vertebrate nervous system. Conformational changes of the transmembrane domain (TMD) underlying ion channel activation and desensitization remain poorly understood. Here, we explored the dynamics of the TMD of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type iGluRs using genetically encoded unnatural amino acid (UAA) photocross-linkers, p-benzoyl-l-phenylalanine (BzF) and p-azido-l-phenylalanine (AzF). We introduced these UAAs at sites throughout the TMD of the GluA2 receptor and characterized the mutants in patch-clamp recordings, exposing them to glutamate and ultraviolet (UV) light. This approach revealed a range of optical effects on the activity of mutant receptors. We found evidence for an interaction between the Pre-M1 and the M4 TMD helix during desensitization. Photoactivation at F579AzF, a residue behind the selectivity filter in the M2 segment, had extraordinarily broad effects on gating and desensitization. This observation suggests coupling to other parts of the receptor and like in other tetrameric ion channels, selectivity filter gating.

scholarly journals The voltage-dependent gate in MthK potassium channels is located at the selectivity filter

2012 ◽  
Vol 20 (2) ◽  
pp. 159-166 ◽  
Author(s):  
David J Posson ◽  
Jason G McCoy ◽  
Crina M Nimigean
Keyword(s):  
Potassium Channels ◽  
Selectivity Filter ◽  
Voltage Dependent

scholarly journals Thermodynamic coupling between activation and inactivation gating in potassium channels revealed by free energy molecular dynamics simulations

2011 ◽  
Vol 138 (6) ◽  
pp. 571-580 ◽  
Author(s):  
Albert C. Pan ◽  
Luis G. Cuello ◽  
Eduardo Perozo ◽  
Benoît Roux
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Molecular Dynamics Simulations ◽  
Conformational Changes ◽  
Ionic Current ◽  
Selectivity Filter ◽  
Recent Analysis ◽  
Steric Interaction ◽  
Inactivation Gating ◽  
Dynamics Simulations

The amount of ionic current flowing through K+ channels is determined by the interplay between two separate time-dependent processes: activation and inactivation gating. Activation is concerned with the stimulus-dependent opening of the main intracellular gate, whereas inactivation is a spontaneous conformational transition of the selectivity filter toward a nonconductive state occurring on a variety of timescales. A recent analysis of multiple x-ray structures of open and partially open KcsA channels revealed the mechanism by which movements of the inner activation gate, formed by the inner helices from the four subunits of the pore domain, bias the conformational changes at the selectivity filter toward a nonconductive inactivated state. This analysis highlighted the important role of Phe103, a residue located along the inner helix, near the hinge position associated with the opening of the intracellular gate. In the present study, we use free energy perturbation molecular dynamics simulations (FEP/MD) to quantitatively elucidate the thermodynamic basis for the coupling between the intracellular gate and the selectivity filter. The results of the FEP/MD calculations are in good agreement with experiments, and further analysis of the repulsive, van der Waals dispersive, and electrostatic free energy contributions reveals that the energetic basis underlying the absence of inactivation in the F103A mutation in KcsA is the absence of the unfavorable steric interaction occurring with the large Ile100 side chain in a neighboring subunit when the intracellular gate is open and the selectivity filter is in a conductive conformation. Macroscopic current analysis shows that the I100A mutant indeed relieves inactivation in KcsA, but to a lesser extent than the F103A mutant.

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