Insights into the mechanisms of transport and regulation of the arabidopsis high-affinity K+ transporter HAK51. Issue 4 (29th January 2021)

• Record Type: Journal Article
• Authors: Ródenas, Reyes; Ragel, Paula; Nieves-Cordones, Manuel; Martínez-Martínez, Almudena; Amo, Jesús; Lara, Alberto; Martínez, Vicente; Quintero, Francisco J; Pardo, Jose M; Rubio, Francisco
• Is Part Of: Plant physiology. Volume 185:Issue 4(2021)
• Page Start: 1860
• Page End: 1874
• Publication Date: 2021-01-29
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1093/plphys/kiab028
• Languages: English
• ISSNs: 0032-0889

Abstract

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