8W9T image
Entry Detail
PDB ID:
8W9T
EMDB ID:
Title:
Structure of TaHKT2;1 in NaCl at 2.6 Angstroms resolution
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2023-09-05
Release Date:
2024-02-14
Method Details:
Experimental Method:
Resolution:
2.60 Å
Aggregation State:
PARTICLE
Reconstruction Method:
SINGLE PARTICLE
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:HKT2
Chain IDs:A, B
Chain Length:544
Number of Molecules:2
Biological Source:Triticum aestivum
Ligand Molecules
Primary Citation
Structures and ion transport mechanisms of plant high-affinity potassium transporters.
Mol Plant 17 409 422 (2024)
PMID: 38335958 DOI: 10.1016/j.molp.2024.01.007

Abstact

Plant high-affinity K+ transporters (HKTs) mediate Na+ and K+ uptake, maintain Na+/K+ homeostasis, and therefore play crucial roles in plant salt tolerance. In this study, we present cryoelectron microscopy structures of HKTs from two classes, class I HKT1;1 from Arabidopsis thaliana (AtHKT1;1) and class II HKT2;1 from Triticum aestivum (TaHKT2;1), in both Na+- and K+-bound states at 2.6- to 3.0-Å resolutions. Both AtHKT1;1 and TaHKT2;1 function as homodimers. Each HKT subunit consists of four tandem domain units (D1-D4) with a repeated K+-channel-like M-P-M topology. In each subunit, D1-D4 assemble into an ion conduction pore with a pseudo-four-fold symmetry. Although both TaHKT2;1 and AtHKT1;1 have only one putative Na+ ion bound in the selectivity filter with a similar coordination pattern, the two HKTs display different K+ binding modes in the filter. TaHKT2;1 has three K+ ions bound in the selectivity filter, but AtHKT1;1 has only two K+ ions bound in the filter, which has a narrowed external entrance due to the presence of a Ser residue in the first filter motif. These structures, along with computational, mutational, and electrophysiological analyses, enable us to pinpoint key residues that are critical for the ion selectivity of HKTs. The findings provide new insights into the ion selectivity and ion transport mechanisms of plant HKTs and improve our understanding about how HKTs mediate plant salt tolerance and enhance crop growth.

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Primary Citation of related structures