Extracellular K+ and Ba2+ mediate voltage‐dependent inactivation of the outward‐rectifying K+ channel encoded by the yeast gene TOK1

Vergani, Paola; Miosga, Thomas; Jarvis, Simon M.; Blatt, Michael R.

doi:10.1016/s0014-5793(97)00211-1

Cited by 35 publications

(65 citation statements)

References 23 publications

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“…The haKAT1:paGFP coding sequence was subcloned into the Xenopus expression vector pBXGS, which includes the Xenopus betaglobin 59-and 39-untranslated sequences, for in vitro transcription and mRNA injection (Groves and Tanner, 1992;Vergani et al, 1997). After 2 to 3 d, oocytes injected with haKAT1:paGFP mRNA expressed protein of ;105 kD that was recognized by monoclonal antibodies to the HA epitope and to GFP ( Figure 1B), consistent with the molecular weight of the haKAT1:paGFP fusion product.…”

Section: Resultssupporting

confidence: 58%

“…Coding sequences for haKAT1:GFP and haKAT1:paGFP were subcloned into the BalI-StuI sites of the plasmid pEXTM1 that includes the 39-and 59-untranslated sequences of the Xenopus etaglobin gene (Vergani et al, 1997) and were verified by sequencing. Plasmids were linearized using HindIII and capped cRNA synthesized in vitro using the mMessage mMachine (Ambion).…”

Section: Xenopus Oocyte Expression and Electrophysiologymentioning

confidence: 99%

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Selective Mobility and Sensitivity to SNAREs Is Exhibited by theArabidopsisKAT1 K+ Channel at the Plasma Membrane

et al. 2006

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Recent findings indicate that proteins in the SNARE superfamily are essential for cell signaling, in addition to facilitating vesicle traffic in plant cell homeostasis, growth, and development. We previously identified SNAREs SYP121/Syr1 from tobacco (Nicotiana tabacum) and the Arabidopsis thaliana homolog SYP121 associated with abscisic acid and drought stress. Disrupting tobacco SYP121 function by expressing a dominant-negative Sp2 fragment had severe effects on growth, development, and traffic to the plasma membrane, and it blocked K þ and Cl ÿ channel responses to abscisic acid in guard cells. These observations raise questions about SNARE control in exocytosis and endocytosis of ion channel proteins and their organization within the plane of the membrane. We have used a dual, in vivo tagging strategy with a photoactivatable green fluorescent protein and externally exposed hemagglutinin epitopes to monitor the distribution and trafficking dynamics of the KAT1 K þ channel transiently expressed in tobacco leaves. KAT1 is localized to the plasma membrane within positionally stable microdomains of ;0.5 mm in diameter; delivery of the K þ channel, but not of the PMA2 H þ -ATPase, to the plasma membrane is suppressed by Sp2 fragments of tobacco and Arabidopsis SYP121, and Sp2 expression leads to profound changes in KAT1 distribution and mobility within the plane of the plasma membrane. These results offer direct evidence for SNARE-mediated traffic of the K þ channel and a role in its distribution within subdomains of the plasma membrane, and they implicate a role for SNAREs in positional anchoring of the K þ channel protein.

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Section: Resultssupporting

confidence: 58%

Section: Xenopus Oocyte Expression and Electrophysiologymentioning

confidence: 99%

Selective Mobility and Sensitivity to SNAREs Is Exhibited by theArabidopsisKAT1 K+ Channel at the Plasma Membrane

et al. 2006

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“…2 Conversely, TOK1 (the 2P/8TM outward rectifier) shows weak voltage dependence and sensitivity to potassium (40,42,58). Recently, Loukin and Saimi (59) showed that TOK1, like Kcnk3, visits two kinetically distinct closed states, a nearly open state (whose dwell time depends on membrane potential and potassium reversal potential), and a deeply closed state (responsive on voltage and external potassium).…”

Section: Time-dependent Changes In Kcnk3 Open Probability Withmentioning

confidence: 99%

Proton Block and Voltage Gating Are Potassium-dependent in the Cardiac Leak Channel Kcnk3

Lopes

Gallagher²,

Buck

et al. 2000

Journal of Biological Chemistry

151

179

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Potassium leak conductances were recently revealed to exist as independent molecular entities. Here, the genomic structure, cardiac localization, and biophysical properties of a murine example are considered. Kcnk3 subunits have two pore-forming P domains and unique functional attributes. At steady state, Kcnk3 channels behave like open, potassium-selective, transmembrane holes that are inhibited by physiological levels of proton. With voltage steps, Kcnk3 channels open and close in two phases, one appears to be immediate and one is time-dependent ( ‫؍‬ ϳ5 ms). Both proton block and gating are potassium-sensitive; this produces an anomalous increase in outward flux as external potassium levels rise because of decreased proton block. Single Kcnk3 channels open across the physiological voltage range; hence they are "leak" conductances; however, they open only briefly and rarely even after exposure to agents that activate other potassium channels.

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“…We have recently succeeded in whole cell patch clamp recordings of the yeast giant protoplasts as well. Thus, a combination of these two methods together shall provide a powerful system for analyzing any ion transporter, not only highly active channels (5)(6)(7)(8)(9)(10)(11)(12)(45)(46)(47)(48) but also other weaker transporters in the membranes, either vacuolar or cytoplasmic, of S. cerevisiae. We used haploid cells because they are much easier than polyploid ones to manipulate genes to yield deletion mutants.…”

Section: H ϩ -Pump Current Of V-type Atpase In Yeast Giant Vacuolesmentioning

confidence: 99%

Patch Clamp Studies on V-type ATPase of Vacuolar Membrane of Haploid Saccharomyces cerevisiae

Yabe¹,

Horiuchi²,

Nakahara³

et al. 1999

Journal of Biological Chemistry

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Complete inhibition at higher concentrations indicated that any other ATP-driven transport systems were not expressed under the present incubation conditions. This current was not observed in the vacuoles prepared from a mutant that disrupted a catalytic subunit of the V-type ATPase (RH105(⌬vma1::TRP)). The K m value for the ATP dose response of the current was 159 M and the H ؉ /ATP ratio estimated from the reversible potential of the V-I curve was 3.5 ؎ 0.3. These values agreed well with those previously estimated by measuring the V-type ATPase activity biochemically. This method can potentially be applied to any type of ion channel, ion pump, and ion transporter in S. cerevisiae, and can also be used to investigate gene functions in various organisms by using yeast cells as hosts for homologous and heterogeneous expression systems.

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Extracellular K⁺ and Ba²⁺ mediate voltage‐dependent inactivation of the outward‐rectifying K⁺ channel encoded by the yeast gene TOK1

Cited by 35 publications

References 23 publications

Selective Mobility and Sensitivity to SNAREs Is Exhibited by theArabidopsisKAT1 K+ Channel at the Plasma Membrane

Selective Mobility and Sensitivity to SNAREs Is Exhibited by theArabidopsisKAT1 K+ Channel at the Plasma Membrane

Proton Block and Voltage Gating Are Potassium-dependent in the Cardiac Leak Channel Kcnk3

Patch Clamp Studies on V-type ATPase of Vacuolar Membrane of Haploid Saccharomyces cerevisiae

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