Reaction kinetic parameters for ion transport from steady-state current-voltage curves

Gradmann, Dietrich; Klieber, Hans-Georg; Hansen, Ulf‐Peter

doi:10.1016/s0006-3495(87)83382-9

Cited by 48 publications

(27 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In effect, this scheme represents a condensed form of the model resolved by Zei and Aldrich (1998) for the wild-type KAT1 channel, in which distal closed states and the isolated burst closed state are subsumed within one or the other of the two dominant states C3 and C2 (Gradmann et al, 1987). We introduced voltage sensitivity to these transitions by assigning a voltage-sensitivity coefficient, d ij , for each reaction constant k ij so that:…”

Section: D105ementioning

confidence: 99%

Voltage-Sensor Transitions of the Inward-Rectifying K+ Channel KAT1 Indicate a Latching Mechanism Biased by Hydration within the Voltage Sensor

et al. 2014

View full text Add to dashboard Cite

The Kv-like (potassium voltage-dependent) K + channels at the plasma membrane, including the inward-rectifying KAT1 K + channel of Arabidopsis (Arabidopsis thaliana), are important targets for manipulating K + homeostasis in plants. Gating modification, especially, has been identified as a promising means by which to engineer plants with improved characteristics in mineral and water use. Understanding plant K + channel gating poses several challenges, despite many similarities to that of mammalian Kv and Shaker channel models. We have used site-directed mutagenesis to explore residues that are thought to form two electrostatic countercharge centers on either side of a conserved phenylalanine (Phe) residue within the S2 and S3 a-helices of the voltage sensor domain (VSD) of Kv channels. Consistent with molecular dynamic simulations of KAT1, we show that the voltage dependence of the channel gate is highly sensitive to manipulations affecting these residues. Mutations of the central Phe residue favored the closed KAT1 channel, whereas mutations affecting the countercharge centers favored the open channel. Modeling of the macroscopic current kinetics also highlighted a substantial difference between the two sets of mutations. We interpret these findings in the context of the effects on hydration of amino acid residues within the VSD and with an inherent bias of the VSD, when hydrated around a central Phe residue, to the closed state of the channel.

show abstract

Section: D105ementioning

confidence: 99%

Voltage-Sensor Transitions of the Inward-Rectifying K+ Channel KAT1 Indicate a Latching Mechanism Biased by Hydration within the Voltage Sensor

et al. 2014

View full text Add to dashboard Cite

show abstract

“…However, the data show that the CHR1 absorption is also protochromic in a lipid environment. (A) Minimum reaction scheme and nomenclature for competitive translocation of H þ and an alternate monovalent cation, here K þ , through an ion translocating enzyme (E) according to Gradmann et al (1987). Voltage-sensitive and temporally resolved reactions between inside and outside can be determined explicitly by steady state current-voltage relationships recorded at different external concentrations of H þ and K þ and are represented by standard line width.…”

Section: Chr1 Spectramentioning

confidence: 99%

Channelrhodopsin-1 Initiates Phototaxis and Photophobic Responses inChlamydomonasby Immediate Light-Induced Depolarization

et al. 2008

View full text Add to dashboard Cite

Channelrhodopsins (CHR1 and CHR2) are light-gated ion channels acting as sensory photoreceptors in Chlamydomonas reinhardtii. In neuroscience, they are used to trigger action potentials by light in neuronal cells, tissues, or living animals. Here, we demonstrate that Chlamydomonas cells with low CHR2 content exhibit photophobic and phototactic responses that strictly depend on the availability of CHR1. Since CHR1 was described as a H þ -channel, the ion specificity of CHR1 was reinvestigated in Xenopus laevis oocytes. Our experiments show that, in addition to H þ , CHR1 also conducts Na þ , K þ , and Ca 2þ . The kinetic selectivity analysis demonstrates that H þ selectivity is not due to specific translocation but due to selective ion binding. Purified recombinant CHR1 consists of two isoforms with different absorption maxima, CHR1 505 and CHR1 463 , that are in pH-dependent equilibrium. Thus, CHR1 is a photochromic and protochromic sensory photoreceptor that functions as a light-activated cation channel mediating phototactic and photophobic responses via depolarizing currents in a wide range of ionic conditions.

show abstract

“…As the data in the present study demonstrate that Na § is not transported through the channel, the Na + loop in the 6-state model (used by Gradmann et al, 1987) has to be interrupted between states 2' and I', i.e., k;,1, and kv2, has to be zero. The voltage sensitivity of the effect of Na + on the K § currents requires the equilibrium constants K1 and K2 to be voltage sensitive.…”

Section: Alternative Modelsmentioning

confidence: 58%

“…In this section, previous theoretical work of Hansen et al (1981) and Gradmann, Klieber & Hansen (1987) is used, extended and applied.…”

Section: Modelingmentioning

confidence: 99%

“…The model used in the present paper can be understood as a special case of the 6-state model presented by Gradmann et al (1987) for the quantitative analysis of current-voltage data from an open K + channel with a finite permeability to Na + as well (kl,2,,k2,v > 0). As the data in the present study demonstrate that Na § is not transported through the channel, the Na + loop in the 6-state model (used by Gradmann et al, 1987) has to be interrupted between states 2' and I', i.e., k;,1, and kv2, has to be zero.…”

Section: Alternative Modelsmentioning

confidence: 99%

See 1 more Smart Citation

Current-voltage relationships of a sodium-sensitive potassium channel in the tonoplast ofChara corallina

Bertl

1989

J. Membrain Biol.

View full text Add to dashboard Cite

Summary, The membrane of mechanically prepared vesicles of Chara corallina has been investigated by patch-clamp techniques. This membrane consists of tonoplast as demonstrated by the measurement of ATP-driven currents directed into the vesicles as well as by the ATP-dependent accumulation of neutral red. Addition of 1 mM ATP to the bath medium induced a membrane current of about 3.2 mA . m 2 creating a voltage across the tonoplast of about -7 mV (cytoplasmic side negative). On excised tonoplast patches, currents through single K*-selective channels have been investigated under various ionic conditions. The open-channel currents saturate at large voltage displacements from the equilibrium voltage for K + with limiting currents of about + 15 and -30 pA, respectively, as measured in symmetric 250 mM KCI solutions. The channel is virtually impermeable to Na + and CI-. However, addition of Na § decreases the K + currents. The 1-V relationships of the open channel as measured at various K + concentrations with or without Na -added are described by a 6-state model, the 12 parameters of which are determined to fit the experimental data.

show abstract

Reaction kinetic parameters for ion transport from steady-state current-voltage curves

Cited by 48 publications

References 22 publications

Voltage-Sensor Transitions of the Inward-Rectifying K+ Channel KAT1 Indicate a Latching Mechanism Biased by Hydration within the Voltage Sensor

Voltage-Sensor Transitions of the Inward-Rectifying K+ Channel KAT1 Indicate a Latching Mechanism Biased by Hydration within the Voltage Sensor

Channelrhodopsin-1 Initiates Phototaxis and Photophobic Responses inChlamydomonasby Immediate Light-Induced Depolarization

Current-voltage relationships of a sodium-sensitive potassium channel in the tonoplast ofChara corallina

Contact Info

Product

Resources

About