Polymer inaccessible volume changes during opening and closing of a voltage-dependent ionic channel

Nature ◽  
1986 ◽  
Vol 323 (6083) ◽  
pp. 36-39 ◽  
Author(s):  
Joshua Zimmerberg ◽  
V. Adrian Parsegian
Keyword(s):  
Ionic Channel ◽  
Volume Changes ◽  
Voltage Dependent ◽  
Opening And Closing

scholarly journals Molecular mechanisms of regulation of fast-inactivating voltage-dependent transient outward K+current in mouse heart by cell volume changes

2005 ◽  
Vol 568 (2) ◽  
pp. 423-443 ◽  
Author(s):  
Guan-Lei Wang ◽  
Ge-Xin Wang ◽  
Shintaro Yamamoto ◽  
Linda Ye ◽  
Heather Baxter ◽  
...  
Keyword(s):  
Cell Volume ◽  
Molecular Mechanisms ◽  
Mouse Heart ◽  
Volume Changes ◽  
Voltage Dependent ◽  
K Current

scholarly journals Major transmembrane movement associated with colicin Ia channel gating.

1996 ◽  
Vol 107 (3) ◽  
pp. 313-328 ◽  
Author(s):  
X Q Qiu ◽  
K S Jakes ◽  
P K Kienker ◽  
A Finkelstein ◽  
S L Slatin
Keyword(s):  
Water Soluble ◽  
Site Directed Mutagenesis ◽  
Lipid Bilayer Membranes ◽  
Transmembrane Segment ◽  
Transmembrane Segments ◽  
Protein Toxin ◽  
Channel Opening ◽  
Voltage Dependent ◽  
Opening And Closing ◽  
Colicin Ia

Colicin Ia, a bacterial protein toxin of 626 amino acid residues, forms voltage-dependent channels in planar lipid bilayer membranes. We have exploited the high affinity binding of streptavidin to biotin to map the topology of the channel-forming domain (roughly 175 residues of the COOH-terminal end) with respect to the membrane. That is, we have determined, for the channel's open and closed states, which parts of this domain are exposed to the aqueous solutions on either side of the membrane and which are inserted into the bilayer. This was done by biotinylating cysteine residues introduced by site-directed mutagenesis, and monitoring by electrophysiological methods the effect of streptavidin addition on channel behavior. We have identified a region of at least 68 residues that flips back and forth across the membrane in association with channel opening and closing. This identification was based on our observations that for mutants biotinylated in this region, streptavidin added to the cis (colicin-containing) compartment interfered with channel opening, and trans streptavidin interfered with channel closing. (If biotin was linked to the colicin by a disulfide bond, the effects of streptavidin on channel closing could be reversed by detaching the streptavidin-biotin complex from the colicin, using a water-soluble reducing agent. This showed that the cysteine sulfur, not just the biotin, is exposed to the trans solution). The upstream and downstream segments flanking the translocated region move into and out of the bilayer during channel opening and closing, forming two transmembrane segments. Surprisingly, if any of several residues near the upstream end of the translocated region is held on the cis side by streptavidin, the colicin still forms voltage-dependent channels, indicating that a part of the protein that normally is fully translocated across the membrane can become the upstream transmembrane segment. Evidently, the identity of the upstream transmembrane segment is not crucial to channel formation, and several open channel structures can exist.

scholarly journals Kinetics of the Opening and Closing of Individual Excitability-Inducing Material Channels in a Lipid Bilayer

1974 ◽  
Vol 63 (6) ◽  
pp. 707-721 ◽  
Author(s):  
Gerald Ehrenstein ◽  
Robert Blumenthal ◽  
Ramon Latorre ◽  
Harold Lecar
Keyword(s):  
Lipid Bilayers ◽  
Ionic Current ◽  
Energy Difference ◽  
Excitable Membranes ◽  
Voltage Dependent ◽  
Ion Conducting ◽  
The Many ◽  
Approach To Steady State ◽  
Opening And Closing ◽  
Kinetics Of

The kinetics of the opening and closing of individual ion-conducting channels in lipid bilayers doped with small amounts of excitability-inducing material (EIM) are determined from discrete fluctuations in ionic current. The kinetics for the approach to steady-state conductance during voltage clamp are determined for lipid bilayers containing many EIM channels. The two sets of measurements are found to be consistent, verifying that the voltage-dependent conductance of the many-channel EIM system arises from the opening and closing of individual EIM channels. The opening and closing of the channels are Poisson processes. Transition rates for these processes vary exponentially with applied potential, implying that the energy difference between the open and closed states of an EIM channel is linearly proportional to the transmembrane electric field. A model incorporating the above properties of the EIM channels predicts the observed voltage dependence of ionic conductance and conductance relaxation time, which are also characteristic of natural electrically excitable membranes.

scholarly journals Cellular function given parametric variation in the Hodgkin and Huxley model of excitability

2018 ◽  
Vol 115 (35) ◽  
pp. E8211-E8218 ◽  
Author(s):  
Hillel Ori ◽  
Eve Marder ◽  
Shimon Marom
Keyword(s):  
Kinetic Parameters ◽  
Physiological Function ◽  
Structural Parameters ◽  
Giant Axon ◽  
Ionic Channels ◽  
Dimensional Representation ◽  
Voltage Dependent ◽  
Parametric Fluctuations ◽  
Opening And Closing ◽  
Activity Dependent

How is reliable physiological function maintained in cells despite considerable variability in the values of key parameters of multiple interacting processes that govern that function? Here, we use the classic Hodgkin–Huxley formulation of the squid giant axon action potential to propose a possible approach to this problem. Although the full Hodgkin–Huxley model is very sensitive to fluctuations that independently occur in its many parameters, the outcome is in fact determined by simple combinations of these parameters along two physiological dimensions: structural and kinetic (denoted S and K, respectively). Structural parameters describe the properties of the cell, including its capacitance and the densities of its ion channels. Kinetic parameters are those that describe the opening and closing of the voltage-dependent conductances. The impacts of parametric fluctuations on the dynamics of the system—seemingly complex in the high-dimensional representation of the Hodgkin–Huxley model—are tractable when examined within the S–K plane. We demonstrate that slow inactivation, a ubiquitous activity-dependent feature of ionic channels, is a powerful local homeostatic control mechanism that stabilizes excitability amid changes in structural and kinetic parameters.

scholarly journals Conductive Properties and Gating of Channels Formed by Syringopeptin 25A, a Bioactive Lipodepsipeptide from Pseudomonas syringae pv. syringae, in Planar Lipid Membranes

1999 ◽  
Vol 12 (5) ◽  
pp. 401-409 ◽  
Author(s):  
Mauro Dalla Serra ◽  
Ivonne Bernhart ◽  
Paola Nordera ◽  
Domenico Di Giorgio ◽  
Alessandro Ballio ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Lipid Membranes ◽  
Pore Radius ◽  
Maximal Conductance ◽  
Channel Opening ◽  
Current Voltage ◽  
Voltage Dependent ◽  
Planar Lipid Membranes ◽  
Opening And Closing ◽  
Conductive Properties

Syringopeptin 25A, a pseudomonad lipodepsipeptide, can form ion channels in planar lipid membranes. Pore conductance is around 40 pS in 0.1 M NaCl. Channel opening is strongly voltage dependent and requires a negative potential on the same side of the membrane where the toxin was added. These pores open and close with a lifetime of several seconds. At negative voltages, an additional pore state of around 10 pS and a lifetime of around 30 ms is also present. The voltage dependence of the rates of opening and closing of the stable pores is exponential. This allows estimation of the equivalent charge that is moved across the membrane during the process of opening at about 2.6 elementary charges. When NaCl is present, the pore is roughly 3 times more permeant for anions than for cations. The current voltage characteristic of the pore is nonlinear, i.e., pore conductance is larger at negative than at positive voltages. The maximal conductance of the pore depends on the concentration of the salt present, in a way that varies almost linearly with the conductivity of the solution. From this, an estimate of a minimal pore radius of 0.4 nm was derived.

scholarly journals Mechanism of gating of T-type calcium channels.

1990 ◽  
Vol 96 (3) ◽  
pp. 603-630 ◽  
Author(s):  
C F Chen ◽  
P Hess
Keyword(s):  
Single Channel ◽  
Ca Channels ◽  
3T3 Fibroblasts ◽  
Channel Inactivation ◽  
Recovery From Inactivation ◽  
Voltage Dependent ◽  
Single Burst ◽  
Opening And Closing ◽  
Rate Limiting ◽  
Kinetics Of

We have analyzed the gating kinetics of T-type Ca channels in 3T3 fibroblasts. Our results show that channel closing, inactivation, and recovery from inactivation each include a voltage-independent step which becomes rate limiting at extreme potentials. The data require a cyclic model with a minimum of two closed, one open, and two inactivated states. Such a model can produce good fits to our data even if the transitions between closed states are the only voltage-dependent steps in the activating pathway leading from closed to inactivated states. Our analysis suggests that the channel inactivation step, as well as the direct opening and closing transitions, are not intrinsically voltage sensitive. Single-channel recordings are consistent with this scheme. As expected, each channel produces a single burst per opening and then inactivates. Comparison of the kinetics of T-type Ca current in fibroblasts and neuronal cells reveals significant differences which suggest that different subtypes of T-type Ca channels are expressed differentially in a tissue specific manner.

scholarly journals New Structures and Gating of Voltage-Dependent Potassium (Kv) Channels and Their Relatives: A Multi-Domain and Dynamic Question

2019 ◽  
Vol 20 (2) ◽  
pp. 248 ◽  
Author(s):  
Francisco Barros ◽  
Luis Pardo ◽  
Pedro Domínguez ◽  
Luisa Sierra ◽  
Pilar de la Peña
Keyword(s):  
General Structure ◽  
Cell Excitability ◽  
Kv Channels ◽  
Transmembrane Voltage ◽  
Voltage Dependent ◽  
Opening And Closing ◽  
Allosteric Mechanisms ◽  
Voltage Sensing Domain ◽  
Pore Domain

Voltage-dependent potassium channels (Kv channels) are crucial regulators of cell excitability that participate in a range of physiological and pathophysiological processes. These channels are molecular machines that display a mechanism (known as gating) for opening and closing a gate located in a pore domain (PD). In Kv channels, this mechanism is triggered and controlled by changes in the magnitude of the transmembrane voltage sensed by a voltage-sensing domain (VSD). In this review, we consider several aspects of the VSD–PD coupling in Kv channels, and in some relatives, that share a common general structure characterized by a single square-shaped ion conduction pore in the center, surrounded by four VSDs located at the periphery. We compile some recent advances in the knowledge of their architecture, based in cryo-electron microscopy (cryo-EM) data for high-resolution determination of their structure, plus some new functional data obtained with channel variants in which the covalent continuity between the VSD and PD modules has been interrupted. These advances and new data bring about some reconsiderations about the use of exclusively a classical electromechanical lever model of VSD–PD coupling by some Kv channels, and open a view of the Kv-type channels as allosteric machines in which gating may be dynamically influenced by some long-range interactional/allosteric mechanisms.

scholarly journals The Nature of the Negative Resistance in Bimolecular Lipid Membranes Containing Excitability-Inducing Material

1970 ◽  
Vol 55 (1) ◽  
pp. 119-133 ◽  
Author(s):  
Gerald Ehrenstein ◽  
Harold Lecar ◽  
Ralph Nossal
Keyword(s):  
Membrane Potential ◽  
Lipid Membranes ◽  
Lipid Membrane ◽  
Negative Resistance ◽  
Voltage Dependent ◽  
The Difference ◽  
Ion Conducting ◽  
Opening And Closing

When sufficiently small amounts of excitability-inducing material (EIM) are added to a bimolecular lipid membrane, the conductance is limited to a few discrete levels and changes abruptly from one level to another. From our study of these fluctuations, we have concluded that the EIM-doped bilayer contains ion-conducting channels capable of undergoing transitions between two states of different conductance. The difference in current between the "open" and "closed" states is directly proportional to the applied membrane potential, and corresponds to a conductance of about 3 x 10-10 ohm-1. The fraction of the total number of channels that is open varies from unity to zero as a function of potential. The voltage-dependent opening and closing of channels explains the negative resistance observed for bimolecular lipid membranes treated with greater amounts of EIM.

Electrical Evidence from Perfused and Intact Cells for Voltage-dependent K+ Channels in the Plasmalemma of Chara australis

1984 ◽  
Vol 11 (4) ◽  
pp. 303 ◽  
Author(s):  
P.T Smith
Keyword(s):  
Steady State ◽  
Negative Slope ◽  
Equilibrium Potential ◽  
Intact Cells ◽  
K Channels ◽  
Current Voltage ◽  
Voltage Dependent ◽  
Chara Australis ◽  
Opening And Closing ◽  
External K

The K+ conductance in Chara australis was studied using current-voltage relations (I- V curves) of intact cells and perfused plasmalemmas in conditions which minimized H+ conductance. The rapid I-V curves of perfused cells were dominated by K+ conductance, intersecting at the calculated K' equilibrium potential. The steady state I-V curves were non-linear; the point of greatest change in slope conductance has been called the 'switch potential'. At voltages more positive than the switch potential, K+ conductance increased with potential. At more negative voltages, K+ conductance was constant and low. In high external K+ concentrations the steady state I-V curves developed negative slope conductance near the switch potential. The switch potential behaved as a function of the KC equilibrium potential. During prolonged voltage pulses in perfused cells, the clamp current changed exponentially with time. The values o f t , were affected by the size of the voltage pulse and the external KT concentration. The results can be explained by time- and voltage-dependent K+ channels. It is suggested that the voltage sensor, which supposedly regulates the opening and closing of the Kt channels, measures a function of the membrane potential and the K+ equilibrium potential.

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