Download MendeleyStructural insights into a citrate transporter that mediates aluminum tolerance in barley.
Nguyen Thao, T., Mitani-Ueno, N., Urano, R., Saitoh, Y., Wang, P., Yamaji, N., Shen, J.R., Shinoda, W., Ma, J.F., Suga, M.(2025) Proc Natl Acad Sci U S A 122: e2501933122-e2501933122
- PubMed: 40763023
- DOI: https://doi.org/10.1073/pnas.2501933122
- Primary Citation of Related Structures:
9L7L - PubMed Abstract:
HvAACT1 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.
- Degree Program in Interdisciplinary Sciences, Graduate School of Environmental, Life, Natural Science, and Technology, Okayama University, Okayama 700-8530, Japan.
Organizational Affiliation:
