9L7L

Structure of the MATE family multidrug resistance transporter HvAACT1 from Hordeum vulgare in the outward-facing state

Summary for 9L7L

• Entry DOI: 10.2210/pdb9l7l/pdb
• Descriptor: HvAACT1 (1 entity in total)
• Functional Keywords: citrate transport, mate protein, membrane protein
• Biological source: Hordeum vulgare
• Total number of polymer chains: 1
• Total formula weight: 49561.55

Authors

Tran, N.T.,Suga, M. (deposition date: 2024-12-26, release date: 2025-08-06, Last modification date: 2025-08-27)

Primary citation

Nguyen Thao, T.,Mitani-Ueno, N.,Urano, R.,Saitoh, Y.,Wang, P.,Yamaji, N.,Shen, J.R.,Shinoda, W.,Ma, J.F.,Suga, M.
Structural insights into a citrate transporter that mediates aluminum tolerance in barley.
Proc.Natl.Acad.Sci.USA, 122:e2501933122-e2501933122, 2025

PubMed Abstract: is a major aluminum (Al)-tolerance gene in barley, encoding a citrate transporter that belongs to the multidrug and toxic compound extrusion (MATE) family. This transporter facilitates citrate secretion from the roots, thereby detoxifying external Al ions-a major constraint of crop production on acidic soils. In this study, we present the outward-facing crystal structure of HvAACT1, providing insights into a citrate transport mechanism. The putative citrate binding site consists of three basic residues-K126 in transmembrane helix 2 (TM2), R358 in TM7, and R535 in TM12-creating substantial positive charges in the C-lobe cavity. Proton coupling for substrate transport may involve two pairs of aspartate residues in the N-lobe cavity, one of which corresponds to the essential Asp pair found in prokaryotic H-coupled MATE transporters belonging to the DinF subfamily. Structural coupling between proton uptake in the N-lobe and citrate extrusion in the C-lobe can be enabled by an extensive, unique hydrogen-bonding network at the extracellular half of the N-lobe. Mutation-based functional analysis, structural comparisons, molecular dynamics simulation, and phylogenic analysis suggest an evolutionary link between citrate MATE transporters and the DinF MATE subfamily. Our findings provide a solid structural basis for citrate transport by HvAACT1 in barley and contribute to a broader understanding of citrate transporter structures in other plant species.

PubMed: 40763023
DOI: 10.1073/pnas.2501933122

Experimental method

X-RAY DIFFRACTION (3.21 Å)