scholarly journals Voltage-Dependent Profile Structures of a Kv-Channel via Time-Resolved Neutron Interferometry

2019 ◽  
Vol 117 (4) ◽  
pp. 751-766 ◽  
Author(s):  
Andrey Y. Tronin ◽  
Lina J. Maciunas ◽  
Kimberly C. Grasty ◽  
Patrick J. Loll ◽  
Haile A. Ambaye ◽  
...  
Keyword(s):  
Neutron Interferometry ◽  
Time Resolved ◽  
Kv Channel ◽  
Voltage Dependent

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.

Expression of voltage-dependent K+ channel genes in mesenteric artery smooth muscle cells

1999 ◽  
Vol 277 (5) ◽  
pp. G1055-G1063 ◽  
Author(s):  
Chuanli Xu ◽  
Yanjie Lu ◽  
Guanghua Tang ◽  
Rui Wang
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Mesenteric Artery ◽  
Muscle Cells ◽  
Mesenteric Arteries ◽  
Delayed Rectifier ◽  
Kv Channel ◽  
Channel Proteins ◽  
Voltage Dependent ◽  
Encoding Genes

Molecular basis of native voltage-dependent K+(Kv) channels in smooth muscle cells (SMCs) from rat mesenteric arteries was investigated. The whole cell patch-clamp study revealed that a 4-aminopyridine-sensitive delayed rectifier K+ current ( I K) was the predominant K+ conductance in these cells. A systematic screening of the expression of 18 Kv channel genes using RT-PCR technique showed that six I K-encoding genes (Kv1.2, Kv1.3, Kv1.5, Kv2.1, Kv2.2, and Kv3.2) were expressed in mesenteric artery. Although no transient outward Kv currents ( I A) were recorded in the studied SMCs, transcripts of multiple I A-encoding genes, including Kv1.4, Kv3.3, Kv3.4, Kv4.1, Kv4.2, and Kv4.3 as well as I A-facilitating Kv β-subunits (Kvβ1, Kvβ2, and Kvβ3), were detected in mesenteric arteries. Western blot analysis demonstrated that four I K-related Kv channel proteins (Kv1.2, Kv1.3, Kv1.5, and Kv2.1) were detected in mesenteric artery tissues. The presence of Kv1.2, Kv1.3, Kv1.5, and Kv2.1 channel proteins in isolated SMCs was further confirmed by immunocytochemistry study. Our results suggest that the native I K in rat mesenteric artery SMCs might be generated by heteromultimerization of Kv genes.

scholarly journals Intrinsic gating properties of a cloned G protein-activated inward rectifier K+ channel.

1995 ◽  
Vol 106 (1) ◽  
pp. 1-23 ◽  
Author(s):  
C A Doupnik ◽  
N F Lim ◽  
P Kofuji ◽  
N Davidson ◽  
H A Lester
Keyword(s):  
G Protein ◽  
K Channel ◽  
Extrinsic Factors ◽  
Time Resolved ◽  
Time Constants ◽  
Protein Activation ◽  
G Protein Activation ◽  
Voltage Dependent ◽  
Current Activation ◽  
Inwardly Rectifying

The voltage-, time-, and K(+)-dependent properties of a G protein-activated inwardly rectifying K+ channel (GIRK1/KGA/Kir3.1) cloned from rat atrium were studied in Xenopus oocytes under two-electrode voltage clamp. During maintained G protein activation and in the presence of high external K+ (VK = 0 mV), voltage jumps from VK to negative membrane potentials activated inward GIRK1 K+ currents with three distinct time-resolved current components. GIRK1 current activation consisted of an instantaneous component that was followed by two components with time constants tau f approximately 50 ms and tau s approximately 400 ms. These activation time constants were weakly voltage dependent, increasing approximately twofold with maximal hyperpolarization from VK. Voltage-dependent GIRK1 availability, revealed by tail currents at -80 mV after long prepulses, was greatest at potentials negative to VK and declined to a plateau of approximately half the maximal level at positive voltages. Voltage-dependent GIRK1 availability shifted with VK and was half maximal at VK -20 mV; the equivalent gating charge was approximately 1.6 e-. The voltage-dependent gating parameters of GIRK1 did not significantly differ for G protein activation by three heterologously expressed signaling pathways: m2 muscarinic receptors, serotonin 1A receptors, or G protein beta 1 gamma 2 subunits. Voltage dependence was also unaffected by agonist concentration. These results indicate that the voltage-dependent gating properties of GIRK1 are not due to extrinsic factors such as agonist-receptor interactions and G protein-channel coupling, but instead are analogous to the intrinsic gating behaviors of other inwardly rectifying K+ channels.

scholarly journals Scanning the Intracellular S6 Activation Gate in the Shaker K+ Channel

2002 ◽  
Vol 119 (6) ◽  
pp. 521-531 ◽  
Author(s):  
David H. Hackos ◽  
Tsg-Hui Chang ◽  
Kenton J. Swartz
Keyword(s):  
Ionic Currents ◽  
K Channel ◽  
Dependent Manner ◽  
Kv Channel ◽  
Closed State ◽  
Kv Channels ◽  
Gate Structure ◽  
Activation Gate ◽  
Voltage Dependent ◽  
Gate Region

In Kv channels, an activation gate is thought to be located near the intracellular entrance to the ion conduction pore. Although the COOH terminus of the S6 segment has been implicated in forming the gate structure, the residues positioned at the occluding part of the gate remain undetermined. We use a mutagenic scanning approach in the Shaker Kv channel, mutating each residue in the S6 gate region (T469-Y485) to alanine, tryptophan, and aspartate to identify positions that are insensitive to mutation and to find mutants that disrupt the gate. Most mutants open in a steeply voltage-dependent manner and close effectively at negative voltages, indicating that the gate structure can both support ion flux when open and prevent it when closed. We find several mutant channels where macroscopic ionic currents are either very small or undetectable, and one mutant that displays constitutive currents at negative voltages. Collective examination of the three types of substitutions support the notion that the intracellular portion of S6 forms an activation gate and identifies V478 and F481 as candidates for occlusion of the pore in the closed state.

scholarly journals Structure of a pore-blocking toxin in complex with a eukaryotic voltage-dependent K+ channel

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Anirban Banerjee ◽  
Alice Lee ◽  
Ernest Campbell ◽  
Roderick MacKinnon
Keyword(s):  
Electron Density ◽  
Selectivity Filter ◽  
K Channel ◽  
Wild Type ◽  
Kv Channel ◽  
Pore Blocking ◽  
Kv Channels ◽  
Filter Structure ◽  
Conduction Pathway ◽  
Voltage Dependent

Pore-blocking toxins inhibit voltage-dependent K+ channels (Kv channels) by plugging the ion-conduction pathway. We have solved the crystal structure of paddle chimera, a Kv channel in complex with charybdotoxin (CTX), a pore-blocking toxin. The toxin binds to the extracellular pore entryway without producing discernable alteration of the selectivity filter structure and is oriented to project its Lys27 into the pore. The most extracellular K+ binding site (S1) is devoid of K+ electron-density when wild-type CTX is bound, but K+ density is present to some extent in a Lys27Met mutant. In crystals with Cs+ replacing K+, S1 electron-density is present even in the presence of Lys27, a finding compatible with the differential effects of Cs+ vs K+ on CTX affinity for the channel. Together, these results show that CTX binds to a K+ channel in a lock and key manner and interacts directly with conducting ions inside the selectivity filter.

scholarly journals Two-stage electro–mechanical coupling of a KV channel in voltage-dependent activation

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Panpan Hou ◽  
Po Wei Kang ◽  
Audrey Deyawe Kongmeneck ◽  
Nien-Du Yang ◽  
Yongfeng Liu ◽  
...  
Keyword(s):  
Two Stage ◽  
Mechanical Coupling ◽  
Kv Channel ◽  
Voltage Dependent

scholarly journals Voltage-dependent gating and gating charge measurements in the Kv1.2 potassium channel

2015 ◽  
Vol 145 (4) ◽  
pp. 345-358 ◽  
Author(s):  
Itzel G. Ishida ◽  
Gisela E. Rangel-Yescas ◽  
Julia Carrasco-Zanini ◽  
León D. Islas
Keyword(s):  
Ion Channels ◽  
Potassium Channel ◽  
Structural Data ◽  
Activation Mechanism ◽  
Voltage Sensitivity ◽  
Structural Interpretation ◽  
Kv Channel ◽  
Gating Charge ◽  
Voltage Dependent ◽  
Electrophysiological Findings

Much has been learned about the voltage sensors of ion channels since the x-ray structure of the mammalian voltage-gated potassium channel Kv1.2 was published in 2005. High resolution structural data of a Kv channel enabled the structural interpretation of numerous electrophysiological findings collected in various ion channels, most notably Shaker, and permitted the development of meticulous computational simulations of the activation mechanism. The fundamental premise for the structural interpretation of functional measurements from Shaker is that this channel and Kv1.2 have the same characteristics, such that correlation of data from both channels would be a trivial task. We tested these assumptions by measuring Kv1.2 voltage-dependent gating and charge per channel. We found that the Kv1.2 gating charge is near 10 elementary charges (eo), ∼25% less than the well-established 13–14 eo in Shaker. Next, we neutralized positive residues in the Kv1.2 S4 transmembrane segment to investigate the cause of the reduction of the gating charge and found that, whereas replacing R1 with glutamine decreased voltage sensitivity to ∼50% of the wild-type channel value, mutation of the subsequent arginines had a much smaller effect. These data are in marked contrast to the effects of charge neutralization in Shaker, where removal of the first four basic residues reduces the gating charge by roughly the same amount. In light of these differences, we propose that the voltage-sensing domains (VSDs) of Kv1.2 and Shaker might undergo the same physical movement, but the septum that separates the aqueous crevices in the VSD of Kv1.2 might be thicker than Shaker’s, accounting for the smaller Kv1.2 gating charge.

A vesicle-trafficking protein commandeers Kv channel voltage sensors for voltage-dependent secretion

Nature Plants ◽  
2015 ◽  
Vol 1 (8) ◽  
Author(s):  
Christopher Grefen ◽  
Rucha Karnik ◽  
Emily Larson ◽  
Cécile Lefoulon ◽  
Yizhou Wang ◽  
...  
Keyword(s):  
Vesicle Trafficking ◽  
Voltage Sensors ◽  
Kv Channel ◽  
Voltage Dependent

scholarly journals Cadmium–cysteine coordination in the BK inner pore region and its structural and functional implications

2015 ◽  
Vol 112 (16) ◽  
pp. 5237-5242 ◽  
Author(s):  
Yu Zhou ◽  
Xiao-Ming Xia ◽  
Christopher J. Lingle
Keyword(s):  
Conformational Changes ◽  
State Dependence ◽  
Bk Channels ◽  
Bk Channel ◽  
Pore Region ◽  
Kv Channel ◽  
Kv Channels ◽  
Voltage Dependent ◽  
Channel Structures ◽  
Inner Pore

To probe structure and gating-associated conformational changes in BK-type potassium (BK) channels, we examined consequences of Cd2+ coordination with cysteines introduced at two positions in the BK inner pore. At V319C, the equivalent of valine in the conserved Kv proline-valine-proline (PVP) motif, Cd2+ forms intrasubunit coordination with a native glutamate E321, which would place the side chains of V319C and E321 much closer together than observed in voltage-dependent K+ (Kv) channel structures, requiring that the proline between V319C and E321 introduces a kink in the BK S6 inner helix sharper than that observed in Kv channel structures. At inner pore position A316C, Cd2+ binds with modest state dependence, suggesting the absence of an ion permeation gate at the cytosolic side of BK channel. These results highlight fundamental structural differences between BK and Kv channels in their inner pore region, which likely underlie differences in voltage-dependent gating between these channels.

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