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.
Highlights
The monovalent cation potassium (K+) plays important roles in various aspects of the life of plants
Based on the gene annotation deposited in the Arabidopsis information resource (TAIR, https://www.arabidopsis.org/) we identified a leucine-rich repeat receptor-like kinase (AT4G18640) among the 60 unique preys (Fig. 1a)
We identified MRH1 to be a pseudokinase that physically interacts with the weak-rectifying K+ channel AKT2
Summary
The monovalent cation potassium (K+) plays important roles in various aspects of the life of plants. One subunit consists of a shorter cytosolic N-terminus, a membrane spanning core with the voltage-sensor module and the pore module, and a larger cytosolic C-terminus This C-terminus can encompass up to 65% of the protein and is highly important for channel tetramerization[8,9,10] and channel regulation[11,12]. AKT2 (AKT2/3) is the only subunit in Arabidopsis that forms Kweak channels and became the model for structure-function and physiological studies on this channel type[16,17,19,20,21,22,25,26,27,28,29,30,31,32] Despite these efforts our knowledge on the regulation of AKT2 is still rudimentary. We speculate that MRH1 may recruit another, so far not identified LRR kinase that exerts the modulatory function on AKT2 in the plant
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
