Insights into the mechanisms of transport and regulation of the arabidopsis high-affinity K+ transporter HAK51

Abstract The high-affinity K+ transporter HAK5 from Arabidopsis (Arabidopsis thaliana) is essential for acquisition and plant growth at low micromolar concentrations. Despite its functional relevance in nutrition, information about domains of scarce. Its activity enhanced by phosphorylation via the AtCIPK23/AtCBL1-9 complex. Based on recently published three-dimensionalstructure bacterial ortholog KimA Bacillus subtilis, we have modeled AtHAK5 and, a mutational approach, identified residues G67, Y70, G71, D72, D201, E312 as function. According to structural model, may bind K+, whereas G71 shape selective filter which resembles that K+shaker-like channels. In addition, show residue S35 AtCIPK23 required reaching maximal transport activity. Serial deletions C-terminus disclosed presence an autoinhibitory domain located between 571 633 together with AtCIPK23-dependent activation downstream position 633. Presumably, autoinhibition counteracted AtCIPK23. Our results provide molecular model describe CIPK-CBL-mediated regulation HAK transporters.