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bioRxiv · 10.64898/2026.10.12.758405

Structural basis for phosphorylation-induced inactivation of the rice ammonium transporter AMT1;1

Yu, F.·Huang, X.·Wang, S.·An, N.·Zhang, P.·Huang, J.·Zhang, X.
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Abstract

Ammonium (NH4+) uptake and transport in plants are mediated by ammonium transporters (AMTs), which are tightly regulated by phosphorylation to prevent excess ammonium influx and toxic accumulation. However, the mechanism of phosphorylation-mediated inactivation is unique and remains unclear. Here, we report cryo-EM structures of the rice (Oryza sativa) ammonium transporter OsAMT1;1 in its wild-type and phosphomimetic variant T452D states. OsAMT1;1 forms a stable homotrimer, with conserved motifs affirming a shared transport mechanism within the AMT/MEP/Rh superfamily. Our structural analysis reveals that T452D phosphomimetic stabilizes an intracellular salt-bridge network and maintains the channel in a closed state, in which the ICL5 loop positions the hydrophobic plug residue Leu360 near the cytoplasmic exit to occlude the channel exit and abolish complementation capacity. Our findings elucidate phosphorylation-induced inactivation mechanism for the plant AMT1 subfamily, providing a structural paradigm for the post-translational regulation of nutrient uptake.

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Yu, F., Huang, X., Wang, S., An, N., Zhang, P., Huang, J., Zhang, X.. 2026-10-12. Structural basis for phosphorylation-induced inactivation of the rice ammonium transporter AMT1;1. https://doi.org/10.64898/2026.10.12.758405

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