@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{NavarroRetamalBremerAlzateMoralesetal.2016,
  author    = {Navarro-Retamal, Carlos and Bremer, Anne and Alzate-Morales, Jans H. and Caballero, Julio and Hincha, Dirk K. and Gonzalez, Wendy and Thalhammer, Anja},
  title     = {Molecular dynamics simulations and CD spectroscopy reveal hydration-induced unfolding of the intrinsically disordered LEA proteins COR15A and COR15B from Arabidopsis thaliana},
  series = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  volume    = {18},
  journal   = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/c6cp02272c},
  pages     = {25806 -- 25816},
  year      = {2016},
  abstract  = {The LEA (late embryogenesis abundant) proteins COR15A and COR15B from Arabidopsis thaliana are intrinsically disordered under fully hydrated conditions, but obtain alpha-helical structure during dehydration, which is reversible upon rehydration. To understand this unusual structural transition, both proteins were investigated by circular dichroism (CD) and molecular dynamics (MD) approaches. MD simulations showed unfolding of the proteins in water, in agreement with CD data obtained with both HIS-tagged and untagged recombinant proteins. Mainly intramolecular hydrogen bonds (H-bonds) formed by the protein backbone were replaced by H-bonds with water molecules. As COR15 proteins function in vivo as protectants in leaves partially dehydrated by freezing, unfolding was further assessed under crowded conditions. Glycerol reduced (40\%) or prevented (100\%) unfolding during MD simulations, in agreement with CD spectroscopy results. H-bonding analysis indicated that preferential exclusion of glycerol from the protein backbone increased stability of the folded state.},
  language  = {en}
}