@article{GarciaMataWangGajdanowiczetal.2010, author = {Garcia-Mata, Carlos and Wang, Jianwen and Gajdanowicz, Pawel and Gonzalez, Wendy and Hills, Adrian and Donald, Naomi and Riedelsberger, Janin and Amtmann, Anna and Dreyer, Ingo and Blatt, Michael R.}, title = {A minimal cysteine motif required to activate the SKOR K+ channel of Arabidopsis by the reactive oxygen species H2O2}, issn = {0021-9258}, doi = {10.1074/jbc.M110.141176}, year = {2010}, abstract = {Reactive oxygen species (ROS) are essential for development and stress signaling in plants. They contribute to plant defense against pathogens, regulate stomatal transpiration, and influence nutrient uptake and partitioning. Although both Ca2+ and K+ channels of plants are known to be affected, virtually nothing is known of the targets for ROS at a molecular level. Here we report that a single cysteine (Cys) residue within the Kv-like SKOR K+ channel of Arabidopsis thaliana is essential for channel sensitivity to the ROS H2O2. We show that H2O2 rapidly enhanced current amplitude and activation kinetics of heterologously expressed SKOR, and the effects were reversed by the reducing agent dithiothreitol (DTT). Both H2O2 and DTT were active at the outer face of the membrane and current enhancement was strongly dependent on membrane depolarization, consistent with a H2O2-sensitive site on the SKOR protein that is exposed to the outside when the channel is in the open conformation. Cys substitutions identified a single residue, Cys(168) located within the S3 alpha-helix of the voltage sensor complex, to be essential for sensitivity to H2O2. The same Cys residue was a primary determinant for current block by covalent Cys S-methioylation with aqueous methanethiosulfonates. These, and additional data identify Cys168 as a critical target for H2O2, and implicate ROS-mediated control of the K+ channel in regulating mineral nutrient partitioning within the plant.}, language = {en} } @phdthesis{Riedelsberger2013, author = {Riedelsberger, Janin}, title = {Functional diversity of plant Shaker-like K+ channels and their regulation}, address = {Potsdam}, pages = {105 S.}, year = {2013}, language = {en} } @article{RiedelsbergerDreyerGonzalez2015, author = {Riedelsberger, Janin and Dreyer, Ingo and Gonzalez, Wendy}, title = {Outward Rectification of Voltage-Gated K+ Channels Evolved at Least Twice in Life History}, series = {PLoS one}, volume = {10}, journal = {PLoS one}, number = {9}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0137600}, pages = {17}, year = {2015}, abstract = {Voltage-gated potassium (K+) channels are present in all living systems. Despite high structural similarities in the transmembrane domains (TMD), this K+ channel type segregates into at least two main functional categories-hyperpolarization-activated, inward-rectifying (Kin) and depolarization-activated, outward-rectifying (Kout) channels. Voltage-gated K+ channels sense the membrane voltage via a voltage-sensing domain that is connected to the conduction pathway of the channel. It has been shown that the voltage-sensing mechanism is the same in Kin and Kout channels, but its performance results in opposite pore conformations. It is not known how the different coupling of voltage-sensor and pore is implemented. Here, we studied sequence and structural data of voltage-gated K+ channels from animals and plants with emphasis on the property of opposite rectification. We identified structural hotspots that alone allow already the distinction between Kin and Kout channels. Among them is a loop between TMD S5 and the pore that is very short in animal Kout, longer in plant and animal Kin and the longest in plant Kout channels. In combination with further structural and phylogenetic analyses this finding suggests that outward-rectification evolved twice and independently in the animal and plant kingdom.}, language = {en} } @misc{RiedelsbergerDreyerGonzalez2015, author = {Riedelsberger, Janin and Dreyer, Ingo and Gonzalez, Wendy}, title = {Outward rectification of voltage-gated K+ channels evolved at least twice in life history}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {521}, issn = {1866-8372}, doi = {10.25932/publishup-40959}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-409594}, pages = {17}, year = {2015}, abstract = {Voltage-gated potassium (K+) channels are present in all living systems. Despite high structural similarities in the transmembrane domains (TMD), this K+ channel type segregates into at least two main functional categories-hyperpolarization-activated, inward-rectifying (Kin) and depolarization-activated, outward-rectifying (Kout) channels. Voltage-gated K+ channels sense the membrane voltage via a voltage-sensing domain that is connected to the conduction pathway of the channel. It has been shown that the voltage-sensing mechanism is the same in Kin and Kout channels, but its performance results in opposite pore conformations. It is not known how the different coupling of voltage-sensor and pore is implemented. Here, we studied sequence and structural data of voltage-gated K+ channels from animals and plants with emphasis on the property of opposite rectification. We identified structural hotspots that alone allow already the distinction between Kin and Kout channels. Among them is a loop between TMD S5 and the pore that is very short in animal Kout, longer in plant and animal Kin and the longest in plant Kout channels. In combination with further structural and phylogenetic analyses this finding suggests that outward-rectification evolved twice and independently in the animal and plant kingdom.}, language = {en} } @article{GonzalezRiedelsbergerMoralesNavarroetal.2012, author = {Gonzalez, Wendy and Riedelsberger, Janin and Morales-Navarro, Samuel E. and Caballero, Julio and Alzate-Morales, Jans H. and Gonzalez-Nilo, Fernando D. and Dreyer, Ingo}, title = {The pH sensor of the plant K+-uptake channel KAT1 is built from a sensory cloud rather than from single key amino acids}, series = {The biochemical journal}, volume = {442}, journal = {The biochemical journal}, number = {7}, publisher = {Portland Press}, address = {London}, issn = {0264-6021}, doi = {10.1042/BJ20111498}, pages = {57 -- 63}, year = {2012}, abstract = {The uptake of potassium ions (K+) accompanied by an acidification of the apoplasm is a prerequisite for stomatal opening. The acidification (approximately 2-2.5 pH units) is perceived by voltage-gated inward potassium channels (K-in) that then can open their pores with lower energy cost. The sensory units for extracellular pH in stomatal K-in channels are proposed to be histidines exposed to the apoplasm. However, in the Arabidopsis thaliana stomatal K-in channel KAT1, mutations in the unique histidine exposed to the solvent (His(267)) do not affect the pH dependency. We demonstrate in the present study that His(267) of the KAT1 channel cannot sense pH changes since the neighbouring residue Phe(266) shifts its pK(a) to undetectable values through a cation-pi interaction. Instead, we show that Glu(240) placed in the extracellular loop between transmembrane segments S5 and S6 is involved in the extracellular acid activation mechanism. Based on structural models we propose that this region may serve as a molecular link between the pH- and the voltage-sensor. Like Glu(240), several other titratable residues could contribute to the pH-sensor of KAT1, interact with each other and even connect such residues far away from the voltage-sensor with the gating machinery of the channel.}, language = {en} } @article{SkłodowskiRiedelsbergerRaddatzetal.2017, author = {Skłodowski, Kamil and Riedelsberger, Janin and Raddatz, Natalia and Riadi, Gonzalo and Caballero, Julio and Ch{\´e}rel, Isabelle and Schulze, Waltraud and Graf, Alexander and Dreyer, Ingo}, title = {The receptor-like pseudokinase MRH1 interacts with the voltage-gated potassium channel AKT2}, series = {Scientific reports}, volume = {7}, journal = {Scientific reports}, publisher = {Nature Publishing Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/srep44611}, pages = {12}, year = {2017}, abstract = {The potassium channel AKT2 plays important roles in phloem loading and unloading. It can operate as inward-rectifying channel that allows H+-ATPase-energized K+ uptake. Moreover, through reversible post-translational modifications it can also function as an open, K+-selective channel, which taps a 'potassium battery', providing additional energy for transmembrane transport processes. Knowledge about proteins involved in the regulation of the operational mode of AKT2 is very limited. Here, we employed a large-scale yeast two-hybrid screen in combination with fluorescence tagging and null-allele mutant phenotype analysis and identified the plasma membrane localized receptor-like kinase MRH1/MDIS2 (AT4G18640) as interaction partner of AKT2. The phenotype of the mrh1-1 knockout plant mirrors that of akt2 knockout plants in energy limiting conditions. Electrophysiological analyses showed that MRH1/MDIS2 failed to exert any functional regulation on AKT2. Using structural protein modeling approaches, we instead gathered evidence that the putative kinase domain of MRH1/MDIS2 lacks essential sites that are indispensable for a functional kinase suggesting that MRH1/MDIS2 is a pseudokinase. We propose that MRH1/MDIS2 and AKT2 are likely parts of a bigger protein complex. MRH1 might help to recruit other, so far unknown partners, which post-translationally regulate AKT2. Additionally, MRH1 might be involved in the recognition of chemical signals.}, language = {en} } @misc{SharmaDreyerRiedelsberger2013, author = {Sharma, Tripti and Dreyer, Ingo and Riedelsberger, Janin}, title = {The role of K+ channels in uptake and redistribution of potassium in the model plant Arabidopsis thaliana}, series = {Frontiers in plant science}, volume = {4}, journal = {Frontiers in plant science}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1664-462X}, doi = {10.3389/fpls.2013.00224}, pages = {16}, year = {2013}, abstract = {Potassium (K+) is inevitable for plant growth and development. It plays a crucial role in the regulation of enzyme activities, in adjusting the electrical membrane potential and the cellular turgor, in regulating cellular homeostasis and in the stabilization of protein synthesis. Uptake of K+ from the soil and its transport to growing organs is essential for a healthy plant development. Uptake and allocation of K+ are performed by K+ channels and transporters belonging to different protein families. In this review we summarize the knowledge on the versatile physiological roles of plant K+ channels and their behavior under stress conditions in the model plant Arabidopsis thaliana.}, language = {en} } @article{LefoulonKarnikHonsbeinetal.2014, author = {Lefoulon, Cecile and Karnik, Rucha and Honsbein, Annegret and Gutla, Paul Vijay and Grefen, Christopher and Riedelsberger, Janin and Poblete, Tomas and Dreyer, Ingo and Gonzalez, Wendy and Blatt, Michael R.}, title = {Voltage-sensor transitions of the inward-rectifying K+ channel KAT1 indicate a latching mechanism biased by hydration within the voltage sensor}, series = {Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants}, volume = {166}, journal = {Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants}, number = {2}, publisher = {American Society of Plant Physiologists}, address = {Rockville}, issn = {0032-0889}, doi = {10.1104/pp.114.244319}, pages = {960 -- U776}, year = {2014}, abstract = {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 alpha-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.}, language = {en} }