The receptor-like pseudokinase MRH1 interacts with the voltage-gated potassium channel AKT2

Sci Rep. 2017 Mar 16:7:44611. doi: 10.1038/srep44611.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Biocatalysis
  • Fluorescence Resonance Energy Transfer
  • Gene Expression Regulation, Plant
  • Gene Knockout Techniques
  • Plant Cells / metabolism
  • Potassium Channels / metabolism*
  • Protein Binding
  • Protein Kinases / metabolism
  • Protein Serine-Threonine Kinases / metabolism*
  • Receptors, Cell Surface / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Reproducibility of Results
  • Saccharomyces cerevisiae / metabolism
  • Xenopus

Substances

  • AKT2 protein, Arabidopsis
  • Arabidopsis Proteins
  • Potassium Channels
  • Receptors, Cell Surface
  • Recombinant Fusion Proteins
  • Protein Kinases
  • MDIS2 protein, Arabidopsis
  • Protein Serine-Threonine Kinases