Conduction and selectivity in potassium channels

Latorre, Ramón; Miller, Christopher

doi:10.1007/bf01870671

Cited by 657 publications

(411 citation statements)

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“…The KAT1 channel shows a higher selectivity for K ÷ versus other alkaline cations (Table 1) than the well-characterized A-type or delayed outward rectifier K ÷ channels from animal cells (Latorre and Miller, 1983;Yool and Schwarz, 1991). A similar selectivity was reported for the inwardly-rectifying K ÷ channel of stomatal guard cells (Blatt, 1992), and for the inward rectifier in starfish egg (Hagiwara and Takahashi, 1974).…”

Section: Caesium and Tetraethylammonium Blocksupporting

confidence: 53%

“…Most of the inwardly-rectifying K ÷ channels characterized in animal cells are the so-called inward rectifiers (Hille, 1992). They display a feature which does not rely upon voltage-gating: their activation potential depends on external K + concentration (Latorre and Miller, 1983). Their inward rectification has often been shown to originate from a block of outward conductance by cytoplasmic Mg 2÷ ions (Matsuda, 1988;Taglialatela eta/., 1994;Vandenberg, 1987).…”

Section: Introductionmentioning

confidence: 99%

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Expression of a cloned plant K⁺ channel in Xenopus oocytes: analysis of macroscopic currents

et al. 1995

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SummaryThe open reading frame from the Arabidopsis thaliana KAT1 cDNA was cloned in a transcription plasmid between the 3' and 5' untranslated regions of a J3-globin cDNA from Xanopus oocyte. The polyedenylated transcripts resulting from in vitro transcription gave rise to high levels of expression of KAT1 channel when injected in Xanopus oocytes. Upon hyperpolarization, a slow activating current could be recorded, inwardly-or outwardly-directed, depending on K + external concentration. Predictions of the voltage-gated channel theory were shown to fit the data well. The equivalent gating charge and the half-activation potential ranged around 2 and -145 mV, respectively. KAT1 gating characteristics did not depend on K + external concentration nor on external pH in the 5.0-7.5 range. KAT1 conductance was, however, increased (40%) when external pH was decreased from 6.5 to 5.0. The apparent affinity constant of KAT1 for K + lay in the range 15-30 raM, at external pH 7.4. As for many K + channels of animal ceils, external caesium caused a voltage-dependent blockage of inward (but not outward) KAT1 current, whereas tetraethylammonium caused a voltage-independent block of both inward and outward KAT1 currents. In conclusion, high levels of expression made it possible to carry out the first quantitative analysis of KAT1 macroscopic currents. KAT1 channel was shown to display features similar to those of as yet uncloned inward-rectifying voltage-gated channels described in both plant cells (namely guard cells) and animal cells.

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Section: Caesium and Tetraethylammonium Blocksupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Expression of a cloned plant K⁺ channel in Xenopus oocytes: analysis of macroscopic currents

et al. 1995

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“…39 ). In this approach, we use a mapping potential of the form (4) where and are two neighboring points on the z axis and E g (z) is the total potential of the systems (i.e. the solvated Na + ) without the constraints.…”

Section: Simulation Methodsmentioning

confidence: 99%

Through the Channel and around the Channel: Validating and Comparing Microscopic Approaches for the Evaluation of Free Energy Profiles for Ion Penetration through Ion Channels

Kato

Warshel

2005

J. Phys. Chem. B

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Microscopic calculations of free energy profiles for ion transport through biological ion channels presents a very serious challenge to modern simulation approaches. The main problem is due to the major convergence problems associated with the heterogeneous landscape of the electrostatic environment in ion channels and with the need to evaluate the profile associated with the transfer of the ion from bulk water to the channel environment. This problem is compounded by the lack of reliable and relevant benchmarks that can discriminate between alternative approaches. The present study is aimed at reducing the above problems by defining benchmarks that are directly relevant to ion channels and can also give converging results. This is done by constructing a series of models of a truncated gramicidin channel with different numbers of water molecules and by comparing the profiles for going around the channel and through the channel. These discriminating models are then used to validate and compare the adiabatic charging free energy perturbation (FEP) approach combined with an umbrella sampling approach (Warshel J. Phys. Chem., 86, 2218Chem., 86, ,1982 and the potential of mean force (PMF) approach used frequently in studies of ion channels. It is found that both approaches work quite well until one moves to the fully solvated channel case. In this limit the PMF approach starts to give different results for the overall work of going through the channel and around the channel while the FEP approach gives physically consistent results. The present benchmark also indicates that the weighted histogram analysis method (WHAM) approach does not offer a significant advantage over earlier approaches at least as much as studies of ion channels are concerned. Finally, it is concluded that the FEP approach may be more useful in evaluating the overall barrier for moving ions from water to ion channels and that in some cases it might be beneficial to use the FEP approach for selective points along the channel and then to connect these points by PMF calculations.

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“…This latter property led Meech (1978) to hypothesize that this conductance system was perfect link between cell metabolism and electrical activity, and he was right on the mark. Because of its large conductance, this voltage and calcium-activated K + channel was christened "maxi K" (Latorre and Miller, 1983) or "BK" (for big K + ; Blatz and Magleby, 1987).…”

Section: Introductionmentioning

confidence: 99%

Large conductance Ca2+-activated K+ (BK) channel: Activation by Ca2+ and voltage

2006

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Large conductance Ca 2+ -activated K + (BK) channels belong to the S4 superfamily of K + channels that include voltage-dependent K + (Kv) channels characterized by having six (S1-S6) transmembrane domains and a positively charged S4 domain. As Kv channels, BK channels contain a S4 domain, but they have an extra (S0) transmembrane domain that leads to an external NH 2 -terminus. The BK channel is activated by internal Ca 2+ , and using chimeric channels and mutagenesis, three distinct Ca 2+ -dependent regulatory mechanisms with different divalent cation selectivity have been identified in its large COOH-terminus. Two of these putative Ca 2+ -binding domains activate the BK channel when cytoplasmic Ca 2+ reaches micromolar concentrations, and a low Ca 2+ affinity mechanism may be involved in the physiological regulation by Mg 2+ . The presence in the BK channel of multiple Ca 2+ -binding sites explains the huge Ca 2+ concentration range (0.1 μM-100 μM) in which the divalent cation influences channel gating. BK channels are also voltage-dependent, and all the experimental evidence points toward the S4 domain as the domain in charge of sensing the voltage. Calcium can open BK channels when all the voltage sensors are in their resting configuration, and voltage is able to activate channels in the complete absence of Ca 2+ . Therefore, Ca 2+ and voltage act independently to enhance channel opening, and this behavior can be explained using a two-tiered allosteric gating mechanism.

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Conduction and selectivity in potassium channels

Cited by 657 publications

References 132 publications

Expression of a cloned plant K⁺ channel in Xenopus oocytes: analysis of macroscopic currents

Expression of a cloned plant K⁺ channel in Xenopus oocytes: analysis of macroscopic currents

Through the Channel and around the Channel: Validating and Comparing Microscopic Approaches for the Evaluation of Free Energy Profiles for Ion Penetration through Ion Channels

Large conductance Ca2+-activated K+ (BK) channel: Activation by Ca2+ and voltage

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Conduction and selectivity in potassium channels

Cited by 657 publications

References 132 publications

Expression of a cloned plant K+ channel in Xenopus oocytes: analysis of macroscopic currents

Expression of a cloned plant K+ channel in Xenopus oocytes: analysis of macroscopic currents

Through the Channel and around the Channel: Validating and Comparing Microscopic Approaches for the Evaluation of Free Energy Profiles for Ion Penetration through Ion Channels

Large conductance Ca2+-activated K+ (BK) channel: Activation by Ca2+ and voltage

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Expression of a cloned plant K⁺ channel in Xenopus oocytes: analysis of macroscopic currents

Expression of a cloned plant K⁺ channel in Xenopus oocytes: analysis of macroscopic currents