Incidence of partial charges on ion selectivity in potassium channels

The conformational changes associated with activation gating in Shaker potassium channels are functionally characterized in patch-clamp recordings made from Xenopus laevis oocytes expressing Shaker channels with fast inactivation removed. Estimates of the forward and backward rates for transitions are obtained by fitting exponentials to macroscopic ionic and gating current relaxations at voltage extremes, where we assume that transitions are unidirectional. The assignment of different rates is facilitated by using voltage protocols that incorporate prepulses to preload channels into different distributions of states, yielding test currents that reflect different subsets of transitions. These data yield direct estimates of the rate constants and partial charges associated with three forward and three backward transitions, as well as estimates of the partial charges associated with other transitions. The partial charges correspond to an average charge movement of 0.5 e0 during each transition in the activation process. This value implies that activation gating involves a large number of transitions to account for the total gating charge displacement of 13 e0. The characterization of the gating transitions here forms the basis for constraining a detailed gating model to be described in a subsequent paper of this series.

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Foldamer-Based Potassium Channels with High Ion Selectivity and Transport Activity

Journal of the American Chemical Society ◽

10.1021/jacs.0c12128 ◽

2021 ◽

Author(s):

Shuaiwei Qi ◽

Chenyang Zhang ◽

Hao Yu ◽

Jing Zhang ◽

Tengfei Yan ◽

...

Keyword(s):

Potassium Channels ◽

Ion Selectivity ◽

Transport Activity

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Faculty Opinions recommendation of Control of ion selectivity in potassium channels by electrostatic and dynamic properties of carbonyl ligands.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1021853.248668 ◽

2004 ◽

Author(s):

D Peter Tieleman

Keyword(s):

Potassium Channels ◽

Dynamic Properties ◽

Ion Selectivity ◽

Carbonyl Ligands

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How Does the W434F Mutation Block Current in Shaker Potassium Channels?

The Journal of General Physiology ◽

10.1085/jgp.109.6.779 ◽

1997 ◽

Vol 109 (6) ◽

pp. 779-789 ◽

Cited By ~ 128

Author(s):

Youshan Yang ◽

Yangyang Yan ◽

Fred J. Sigworth

Keyword(s):

Potassium Channels ◽

Potassium Current ◽

Xenopus Oocytes ◽

Single Channel ◽

Ion Selectivity ◽

Independent Component ◽

Single Channel Recordings ◽

Shaker Channels ◽

Rapid Inactivation ◽

Shaker Potassium Channels

The mutation W434F produces an apparently complete block of potassium current in Shaker channels expressed in Xenopus oocytes. Tandem tetrameric constructs containing one or two subunits with this mutation showed rapid inactivation, although the NH2-terminal inactivation domain was absent from these constructs. The inactivation showed a selective dependence on external cations and was slowed by external TEA; these properties are characteristic of C-type inactivation. Inactivation was, however, incompletely relieved by hyperpolarization, suggesting the presence of a voltage-independent component. The hybrid channels had near-normal conductance and ion selectivity. Single-channel recordings from patches containing many W434F channels showed occasional channel openings, consistent with open probabilities of 10−5 or less. We conclude that the W434F mutation produces a channel that is predominantly found in an inactivated state.

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