scholarly journals A Mutation in S6 of Shaker Potassium Channels Decreases the K+ Affinity of an Ion Binding Site Revealing Ion–Ion Interactions in the Pore

1998 ◽  
Vol 112 (2) ◽  
pp. 243-257 ◽  
Author(s):  
Eva M. Ogielska ◽  
Richard W. Aldrich
Keyword(s):  
Potassium Channels ◽  
Potassium Channel ◽  
Binding Site ◽  
Sodium Current ◽  
High Potassium ◽  
Independent Evidence ◽  
Channel Pore ◽  
Shaker Potassium Channel ◽  
Ion Interactions ◽  
Barium Block

Under physiological conditions, potassium channels are extraordinarily selective for potassium over other ions. However, in the absence of potassium, certain potassium channels can conduct sodium. Sodium flux is blocked by the addition of low concentrations of potassium. Potassium affinity, and therefore the ability to block sodium current, varies among potassium channel subtypes (Korn, S.J., and S.R. Ikeda. 1995. Science. 269:410–412; Starkus, J.G., L. Kuschel, M.D. Rayner, and S.H. Heinemann. 1997. J. Gen. Physiol. 110:539–550). The Shaker potassium channel conducts sodium poorly in the presence of very low (micromolar) potassium due to its high potassium affinity (Starkus, J.G., L. Kuschel, M.D. Rayner, and S.H. Heinemann. 1997. J. Gen. Physiol. 110:539–550; Ogielska, E.M., and R.W. Aldrich. 1997. Biophys. J. 72:A233 [Abstr.]). We show that changing a single residue in S6, A463C, decreases the apparent internal potassium affinity of the Shaker channel pore from the micromolar to the millimolar range, as determined from the ability of potassium to block the sodium currents. Independent evidence that A463C decreases the apparent affinity of a binding site in the pore comes from a study of barium block of potassium currents. The A463C mutation decreases the internal barium affinity of the channel, as expected if barium blocks current by binding to a potassium site in the pore. The decrease in the apparent potassium affinity in A463C channels allows further study of possible ion interactions in the pore. Our results indicate that sodium and potassium can occupy the pore simultaneously and that multiple occupancy results in interactions between ions in the channel pore.

scholarly journals Polyamine block of MthK potassium channels

2020 ◽  
Vol 152 (7) ◽  
Author(s):  
Crina M. Nimigean
Keyword(s):  
Ion Channels ◽  
Potassium Channels ◽  
Potassium Channel ◽  
Binding Site ◽  
Ion Flux ◽  
Membrane Excitability ◽  
Channel Pore

Polyamines can modulate membrane excitability by blocking ion flux through ion channels. Suma et al. determined the location of the binding site for polyamines inside a model potassium channel pore.

Use of voltage clamp fluorimetry in understanding potassium channel gating: a review of Shaker fluorescence data

2009 ◽  
Vol 87 (6) ◽  
pp. 411-418 ◽  
Author(s):  
A.J. Horne ◽  
D. Fedida
Keyword(s):  
Potassium Channels ◽  
Potassium Channel ◽  
Voltage Clamp ◽  
Channel Gating ◽  
Specific Protein ◽  
Channel Activation ◽  
Shaker Potassium Channel ◽  
Inactivation Gating ◽  
Nanosecond Time Resolution ◽  
Shaker Potassium Channels

Voltage clamp fluorimetry (VCF) utilizes fluorescent probes that covalently bind to cysteine residues introduced into proteins and emit light as a function of their environment. Measurement of this emitted light during membrane depolarization reveals changes in the emission level as the environment of the labelled residue changes. This allows for the correlation of channel gating events with movement of specific protein moieties, at nanosecond time resolution. Since the pioneering use of this technique to investigate Shaker potassium channel activation movements, VCF has become an invaluable technique used to understand ion channel gating. This review summarizes the theory and some of the data on the application of the VCF technique. Although its usage has expanded beyond voltage-gated potassium channels and VCF is now used in a number of other voltage- and ligand-gated channels, we will focus on studies conducted in Shaker potassium channels, and what they have told us about channel activation and inactivation gating.

scholarly journals On the role of ball and chain interactions in recovery from the inactivation of the shaker potassium channel

2008 ◽  
Vol 13 (4) ◽  
Author(s):  
Przemysław Borys ◽  
Zbigniew Grzywna
Keyword(s):  
Potassium Channel ◽  
Binding Site ◽  
Chain Model ◽  
Shaker Potassium Channel ◽  
Recovery From Inactivation

AbstractWe describe a new factor in the recovery from inactivation in the ball and chain model. We propose a model in which the tension from the chain may help pull the ball away from its binding site, reducing the duration of the inactivation period. A corresponding model was built and analysed.

scholarly journals Functional Consequences of a Decreased Potassium Affinity in a Potassium Channel Pore

1999 ◽  
Vol 113 (2) ◽  
pp. 347-358 ◽  
Author(s):  
Eva M. Ogielska ◽  
Richard W. Aldrich
Keyword(s):  
Potassium Channel ◽  
Binding Site ◽  
Conformational Change ◽  
Electrostatic Interactions ◽  
Selectivity Filter ◽  
Inactivation Rate ◽  
Ion Binding ◽  
Present Evidence ◽  
Channel Pore ◽  
Functional Consequences

Ions bound near the external mouth of the potassium channel pore impede the C-type inactivation conformational change (Lopez-Barneo, J., T. Hoshi, S. Heinemann, and R. Aldrich. 1993. Receptors Channels. 1:61– 71; Baukrowitz, T., and G. Yellen. 1995. Neuron. 15:951–960). In this study, we present evidence that the occupancy of the C-type inactivation modulatory site by permeant ions is not solely dependent on its intrinsic affinity, but is also a function of the relative affinities of the neighboring sites in the potassium channel pore. The A463C mutation in the S6 region of Shaker decreases the affinity of an internal ion binding site in the pore (Ogielska, E.M., and R.W. Aldrich, 1998). However, we have found that this mutation also decreases the C-type inactivation rate of the channel. Our studies indicate that the C-type inactivation effects observed with substitutions at position A463 most likely result from changes in the pore occupancy of the channel, rather than a change in the C-type inactivation conformational change. We have found that a decrease in the potassium affinity of the internal ion binding site in the pore results in lowered (electrostatic) interactions among ions in the pore and as a result prolongs the time an ion remains bound at the external C-type inactivation site. We also present evidence that the C-type inactivation constriction is quite local and does not involve a general collapse of the selectivity filter. Our data indicate that in A463C potassium can bind within the selectivity filter without interfering with the process of C-type inactivation.

scholarly journals Agitoxin Footprinting the Shaker Potassium Channel Pore

Neuron ◽  
1996 ◽  
Vol 16 (2) ◽  
pp. 399-406 ◽  
Author(s):  
Adrian Gross ◽  
Roderick MacKinnon
Keyword(s):  
Potassium Channel ◽  
Channel Pore ◽  
Shaker Potassium Channel

scholarly journals Remodeling of Arterial Tone Regulation in Postnatal Development: Focus on Smooth Muscle Cell Potassium Channels

2021 ◽  
Vol 22 (11) ◽  
pp. 5413
Author(s):  
Anastasia A. Shvetsova ◽  
Dina K. Gaynullina ◽  
Olga S. Tarasova ◽  
Rudolf Schubert
Keyword(s):  
Smooth Muscle ◽  
Potassium Channels ◽  
Potassium Channel ◽  
Postnatal Development ◽  
Sympathetic Innervation ◽  
Treatment Strategies ◽  
Muscle Membrane ◽  
Postnatal Life ◽  
Vascular Control ◽  
Bkca Channels

Maturation of the cardiovascular system is associated with crucial structural and functional remodeling. Thickening of the arterial wall, maturation of the sympathetic innervation, and switching of the mechanisms of arterial contraction from calcium-independent to calcium-dependent occur during postnatal development. All these processes promote an almost doubling of blood pressure from the moment of birth to reaching adulthood. This review focuses on the developmental alterations of potassium channels functioning as key smooth muscle membrane potential determinants and, consequently, vascular tone regulators. We present evidence that the pattern of potassium channel contribution to vascular control changes from Kir2, Kv1, Kv7 and TASK-1 channels to BKCa channels with maturation. The differences in the contribution of potassium channels to vasomotor tone at different stages of postnatal life should be considered in treatment strategies of cardiovascular diseases associated with potassium channel malfunction.

Sign in / Sign up

Export Citation Format

Share Document