Cloning and electrophysiological analysis of KST1, an inward rectifying K+ channel expressed in potato guard cells.

Müller‐Röber, Bernd; Ellenberg, Jan; Provart, Nicholas J.; Willmitzer, Lothar; Busch, H.; Becker, Dirk; Dietrich, Petra; Hoth, Stefan; Hedrich, Rainer

doi:10.1002/j.1460-2075.1995.tb07238.x

Cited by 207 publications

(204 citation statements)

References 38 publications

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“…Based on the current molecular model of the Shaker channel we were able to relate structural elements of guard cell K ϩ inward rectifiers to stomatal physiology. In this context we have previously shown that a putative ATP-binding site in the amino acid sequence together with the requirement of KST1 for cytoplasmic ATP pointed to a tight coupling between channel activity and guard cell energy metabolism (12).Here, we demonstrate that protonation and deprotonation in response to the H ϩ pumping activity and acid metabolism modulates the K ϩ uptake channel. Proton-induced increase in whole cell currents of KST1 is due to a shift in the halfmaximum activation voltage rather than an increase in the single-channel conductance.…”

mentioning

confidence: 54%

“…Hydrophobicity analyses of their primary structure predicted six transmembrane domains (S1-S6) (12,16,17). Whereas S4 is likely to represent the voltage sensor of these voltage-dependent channels, the amphiphilic linker between S5 and S6 (P) forms the conductive pore (18).…”

Section: Introductionmentioning

confidence: 99%

“…Within this range changes in the extracellular proton concentration affect the activity of guard cell inward rectifying K ϩ channels (10-13). In contrast to their functional and structural animal counterparts, which are either not activated or even inhibited by protons (14, 15), the guard cell K ϩ channel is activated upon extracellular acidification (10-13).The molecular cloning of plant K ϩ inward rectifiers revealed a structural homology to animal outward rectifying K ϩ channels of the Shaker gene family (12,16,17). Hydrophobicity analyses of their primary structure predicted six transmembrane domains (S1-S6) (12,16,17).…”

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Molecular basis of plant-specific acid activation of K ⁺ uptake channels

Hoth¹,

Drèyer²,

Dietrich³

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

123

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During stomatal opening potassium uptake into guard cells and K ؉ channel activation is tightly coupled to proton extrusion. The pH sensor of the K ؉ uptake channel in these motor cells has, however, not yet been identified. Electrophysiological investigations on the voltage-gated, inward rectifying K ؉ channel in guard cell protoplasts from Solanum tuberosum (KST1), and the kst1 gene product expressed in Xenopus oocytes revealed that pH dependence is an intrinsic property of the channel protein. Whereas extracellular acidification resulted in a shift of the voltage-dependence toward less negative voltages, the single-channel conductance was pH-insensitive. Mutational analysis allowed us to relate this acid activation to both extracellular histidines in KST1. One histidine is located within the linker between the transmembrane helices S3 and S4 (H160), and the other within the putative pore-forming region P between S5 and S6 (H271). When both histidines were substituted by alanines the double mutant completely lost its pH sensitivity. Among the single mutants, replacement of the pore histidine, which is highly conserved in plant K ؉ channels, increased or even inverted the pH sensitivity of KST1. From our molecular and biophysical analyses we conclude that both extracellular sites are part of the pH sensor in plant K ؉ uptake channels.Plant growth, differentiation, cell and tissue polarity, as well as movements strongly depend on the formation of pH gradients across individual cell types (1-3). Stomata that are formed by two guard cells represent a unique model for plant movement. Regulation of stomatal movement in higher plants is essential for efficient uptake of CO 2 at minimal water loss. Stomatal opening requires accumulation of potassium ions into guard cells. K ϩ uptake is mediated by K ϩ uptake channels, a process accompanied by the acidification of the apoplast (4-7). Due to differential pumping activity of the plasma membrane H ϩ -pump the apoplastic pH around closed and open stomata varies between 7 and 5 (8, 9). Within this range changes in the extracellular proton concentration affect the activity of guard cell inward rectifying K ϩ channels (10-13). In contrast to their functional and structural animal counterparts, which are either not activated or even inhibited by protons (14, 15), the guard cell K ϩ channel is activated upon extracellular acidification (10-13).The molecular cloning of plant K ϩ inward rectifiers revealed a structural homology to animal outward rectifying K ϩ channels of the Shaker gene family (12,16,17). Hydrophobicity analyses of their primary structure predicted six transmembrane domains (S1-S6) (12,16,17). Whereas S4 is likely to represent the voltage sensor of these voltage-dependent channels, the amphiphilic linker between S5 and S6 (P) forms the conductive pore (18). Based on the current molecular model of the Shaker channel we were able to relate structural elements of guard cell K ϩ inward rectifiers to stomatal physiology. In this context we have previously sho...

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mentioning

confidence: 54%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Molecular basis of plant-specific acid activation of K ⁺ uptake channels

Hoth¹,

Drèyer²,

Dietrich³

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

123

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“…Due to the latter fact, it is likely that the Ca 2+ insensitivity is a characteristic feature of the Arabidopsis channel KAT1 rather than an attribute of the expression system. Nevertheless, the reliability of the data concerning properties obtained in heterologous expression systems remains uncertain until like for KST1 [18] information about the in vivo channel characteristics is available for KAT1, too.…”

Section: Resultsmentioning

confidence: 99%

“…On the molecular level the plant inward rectifiers are represented by transporters belonging to the family of KAT1-and AKTl-related channels [1,23]. So far, a functional analysis of an inwardly-rectifying K + channel in vivo as well as in vitro was only performed for a guard cell K ÷ uptake channel identified in potato, and the related channel gene product KST1 [18]. For the comparative studies, KST1 was expressed in Xenopus oocytes, whereas isolated potato guard cells were used as the in vivo system.…”

Section: Introductionmentioning

confidence: 99%