8w9o

structure of AtHKT1;1 in KCl at 2.8 Angstroms resolutionstructure of AtHKT1;1 in KCl at 2.8 Angstroms resolution

Structural highlights

8w9o is a 2 chain structure with sequence from Arabidopsis thaliana. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	Electron Microscopy, Resolution 2.8Å
Ligands:
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

HKT1_ARATH Sodium transporter protein, which plays a central role in plant tolerance to salt. Upon prolongated exposure to high concentrations, Na(+) translocates from the roots to the transpiring leaves where it can increase to toxic level. Involved in Na(+) recirculation from shoots to roots, probably by mediating Na(+) loading into the phloem sap in shoots and unloading in roots, thereby removing large amounts of Na(+) from the shoot. Does not transport K(+) but regulates K(+) nutrient status via its ability to facilitate Na(+) homeostasis. Probably not involved in root uptake of Na(+).^[1] ^[2] ^[3] ^[4] ^[5] ^[6] ^[7]

Publication Abstract from PubMed

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-A 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.

Structures and ion transport mechanisms of plant high-affinity potassium transporters.,Wang J, Luo Y, Ye F, Ding ZJ, Zheng SJ, Qiao S, Wang Y, Guo J, Yang W, Su N Mol Plant. 2024 Mar 4;17(3):409-422. doi: 10.1016/j.molp.2024.01.007. Epub 2024 , Feb 8. PMID:38335958^[8]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Uozumi N, Kim EJ, Rubio F, Yamaguchi T, Muto S, Tsuboi A, Bakker EP, Nakamura T, Schroeder JI. The Arabidopsis HKT1 gene homolog mediates inward Na(+) currents in xenopus laevis oocytes and Na(+) uptake in Saccharomyces cerevisiae. Plant Physiol. 2000 Apr;122(4):1249-59. PMID:10759522 doi:10.1104/pp.122.4.1249
↑ Rus A, Yokoi S, Sharkhuu A, Reddy M, Lee BH, Matsumoto TK, Koiwa H, Zhu JK, Bressan RA, Hasegawa PM. AtHKT1 is a salt tolerance determinant that controls Na(+) entry into plant roots. Proc Natl Acad Sci U S A. 2001 Nov 20;98(24):14150-5. PMID:11698666 doi:10.1073/pnas.241501798
↑ Mäser P, Hosoo Y, Goshima S, Horie T, Eckelman B, Yamada K, Yoshida K, Bakker EP, Shinmyo A, Oiki S, Schroeder JI, Uozumi N. Glycine residues in potassium channel-like selectivity filters determine potassium selectivity in four-loop-per-subunit HKT transporters from plants. Proc Natl Acad Sci U S A. 2002 Apr 30;99(9):6428-33. PMID:11959905 doi:10.1073/pnas.082123799
↑ Mäser P, Eckelman B, Vaidyanathan R, Horie T, Fairbairn DJ, Kubo M, Yamagami M, Yamaguchi K, Nishimura M, Uozumi N, Robertson W, Sussman MR, Schroeder JI. Altered shoot/root Na+ distribution and bifurcating salt sensitivity in Arabidopsis by genetic disruption of the Na+ transporter AtHKT1. FEBS Lett. 2002 Nov 6;531(2):157-61. PMID:12417304 doi:10.1016/s0014-5793(02)03488-9
↑ Berthomieu P, Conéjéro G, Nublat A, Brackenbury WJ, Lambert C, Savio C, Uozumi N, Oiki S, Yamada K, Cellier F, Gosti F, Simonneau T, Essah PA, Tester M, Véry AA, Sentenac H, Casse F. Functional analysis of AtHKT1 in Arabidopsis shows that Na(+) recirculation by the phloem is crucial for salt tolerance. EMBO J. 2003 May 1;22(9):2004-14. PMID:12727868 doi:10.1093/emboj/cdg207
↑ Rus A, Lee BH, Muñoz-Mayor A, Sharkhuu A, Miura K, Zhu JK, Bressan RA, Hasegawa PM. AtHKT1 facilitates Na+ homeostasis and K+ nutrition in planta. Plant Physiol. 2004 Sep;136(1):2500-11. PMID:15347798 doi:10.1104/pp.104.042234
↑ Gong JM, Waner DA, Horie T, Li SL, Horie R, Abid KB, Schroeder JI. Microarray-based rapid cloning of an ion accumulation deletion mutant in Arabidopsis thaliana. Proc Natl Acad Sci U S A. 2004 Oct 26;101(43):15404-9. PMID:15486089 doi:10.1073/pnas.0404780101
↑ Wang J, Luo Y, Ye F, Ding ZJ, Zheng SJ, Qiao S, Wang Y, Guo J, Yang W, Su N. Structures and ion transport mechanisms of plant high-affinity potassium transporters. Mol Plant. 2024 Mar 4;17(3):409-422. PMID:38335958 doi:10.1016/j.molp.2024.01.007

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OCA

[1] Uozumi N, Kim EJ, Rubio F, Yamaguchi T, Muto S, Tsuboi A, Bakker EP, Nakamura T, Schroeder JI. The Arabidopsis HKT1 gene homolog mediates inward Na(+) currents in xenopus laevis oocytes and Na(+) uptake in Saccharomyces cerevisiae. Plant Physiol. 2000 Apr;122(4):1249-59. PMID:10759522 doi:10.1104/pp.122.4.1249

[2] Rus A, Yokoi S, Sharkhuu A, Reddy M, Lee BH, Matsumoto TK, Koiwa H, Zhu JK, Bressan RA, Hasegawa PM. AtHKT1 is a salt tolerance determinant that controls Na(+) entry into plant roots. Proc Natl Acad Sci U S A. 2001 Nov 20;98(24):14150-5. PMID:11698666 doi:10.1073/pnas.241501798

[3] Mäser P, Hosoo Y, Goshima S, Horie T, Eckelman B, Yamada K, Yoshida K, Bakker EP, Shinmyo A, Oiki S, Schroeder JI, Uozumi N. Glycine residues in potassium channel-like selectivity filters determine potassium selectivity in four-loop-per-subunit HKT transporters from plants. Proc Natl Acad Sci U S A. 2002 Apr 30;99(9):6428-33. PMID:11959905 doi:10.1073/pnas.082123799

[4] Mäser P, Eckelman B, Vaidyanathan R, Horie T, Fairbairn DJ, Kubo M, Yamagami M, Yamaguchi K, Nishimura M, Uozumi N, Robertson W, Sussman MR, Schroeder JI. Altered shoot/root Na+ distribution and bifurcating salt sensitivity in Arabidopsis by genetic disruption of the Na+ transporter AtHKT1. FEBS Lett. 2002 Nov 6;531(2):157-61. PMID:12417304 doi:10.1016/s0014-5793(02)03488-9

[5] Berthomieu P, Conéjéro G, Nublat A, Brackenbury WJ, Lambert C, Savio C, Uozumi N, Oiki S, Yamada K, Cellier F, Gosti F, Simonneau T, Essah PA, Tester M, Véry AA, Sentenac H, Casse F. Functional analysis of AtHKT1 in Arabidopsis shows that Na(+) recirculation by the phloem is crucial for salt tolerance. EMBO J. 2003 May 1;22(9):2004-14. PMID:12727868 doi:10.1093/emboj/cdg207

[6] Rus A, Lee BH, Muñoz-Mayor A, Sharkhuu A, Miura K, Zhu JK, Bressan RA, Hasegawa PM. AtHKT1 facilitates Na+ homeostasis and K+ nutrition in planta. Plant Physiol. 2004 Sep;136(1):2500-11. PMID:15347798 doi:10.1104/pp.104.042234

[7] Gong JM, Waner DA, Horie T, Li SL, Horie R, Abid KB, Schroeder JI. Microarray-based rapid cloning of an ion accumulation deletion mutant in Arabidopsis thaliana. Proc Natl Acad Sci U S A. 2004 Oct 26;101(43):15404-9. PMID:15486089 doi:10.1073/pnas.0404780101

[8] Wang J, Luo Y, Ye F, Ding ZJ, Zheng SJ, Qiao S, Wang Y, Guo J, Yang W, Su N. Structures and ion transport mechanisms of plant high-affinity potassium transporters. Mol Plant. 2024 Mar 4;17(3):409-422. PMID:38335958 doi:10.1016/j.molp.2024.01.007

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