Biophysical bases and the physiological implications of the posttranslational regulation of the Arabidopsis thaliana K+ channel AKT2

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AKT2 is unique among potassium channels in the model plant Arabidopsis thaliana. This voltage-gated K+ channel has exceptional gating properties that are strongly regulated by posttranslational modifications as e.g. phosphorylation. When nonphosphorylated AKT2 behaves as an inward-rectifying potassium channel mediating K+ uptake only. In its phosphorylated form, however, AKT2 is locked open and can therefore transport K+ in both directions over the plasmamembrane. Although recent publications provided first insights into the unique gating of AKT2, its regulation as well as the physiological implications of this regulation are still matter of debate.This proposal, which is based on three recent own publications, was designed to clarify certain aspects of the regulation of the activity of AKT2. The planned work combines biophysical, molecular biological, plant physiological, biochemical and computational simulation approaches. It involves the generation of mutated AKT2 channels and their analyses in heterologous expression systems, the analysis of transgenic plants expressing mutated AKT2 channels and the biochemical identification of posttranslational modifications at the AKT2 protein. The results of these experiments will be complemented with computational simulations to model the electrical behavior of plant cells expressing AKT2. The combined results of the different approaches will allow to develop a detailed picture on the physiological role of the unique K+ channel AKT2.