Structural insight into the Arabidopsis vacuolar anion channel ALMT9 shows clade specificity

• DOI: 10.1016/j.celrep.2024.114731
• Publication Date: 2024-09-12T09:22:14Z
• Authors: Dandan Qian; Yaru Chai; Weiping Li; Bin Cui; Shaoquan Lin; Zhibin Wang; Chongyuan Wang; Le Qing Qu; Deshun Gong

The Arabidopsis thaliana aluminum-activated malate transporter 9 (AtALMT9) functions as a vacuolar chloride channel that regulates the stomatal aperture. Here, we present cryoelectron microscopy (cryo-EM) structures of AtALMT9 in three distinct states. forms dimer, and pore is lined with four positively charged rings. apo-AtALMT9 state shows putative endogenous citrate obstructing pore, where two W120 constriction residues enclose gate radius approximately 1.8 Å, representing an open state. Interestingly, closure solely controlled by W120. Compared to wild-type plants, W120A mutant exhibits more sensitivity drought stress unable restore visual phenotype on leaves upon water recovery, reflecting persistent opening. Furthermore, notable variations are noted gating substrate recognition Glycine max ALMT12, AtALMT9, AtALMT1. In summary, our investigation enhances comprehension interplay between structure function within ALMT family.