Molecular basis for the R-type anion channel QUAC1 activity in guard cells

Qin, L.; Tang, L.-h.; Xu, J.-s.; Zhang, X.-h.; Zhu, Y.; Zhang, C.-r.; Liu, X.-l.; Wang, M.-h.; Li, F.; Sun, F.; Su, M.; Zhai, Y.-J.; Chen, Y.-h.

doi:10.1101/2021.09.09.459598

bioRxiv · 10.1101/2021.09.09.459598

Molecular basis for the R-type anion channel QUAC1 activity in guard cells

Qin, L.·Tang, L.-h.·Xu, J.-s.·Zhang, X.-h.·Zhu, Y.·Zhang, C.-r.·Liu, X.-l.·Wang, M.-h.·Li, F.·Sun, F.·Su, M.·Zhai, Y.-J.·Chen, Y.-h.

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Abstract

The rapid (R)-type anion channel plays a central role in controlling stomatal closure in plant guard cells, thus regulating the exchange of water and photosynthetic gas (CO2) in response to environmental stimuli. The activity of the R- type anion channel is regulated by malate. However, the molecular basis of the R-type anion channel activity remains elusive. Here, we describe the first cryo-EM structure of the R-type anion channel QUAC1 at 3.5 [A] resolution in the presence of malate. The structure reveals that the QUAC1 is a symmetrical dimer, forming a single electropositive T-shaped pore for passing anions across the membrane. The transmembrane and cytoplasmic domains are assembled into a twisted bi-layer architecture, with the associated dimeric interfaces nearly perpendicular. Our structural and functional analyses reveal that QUAC1 functions as an inward rectifying anion channel and suggests a mechanism for malate-mediated channel activation. Altogether, our study uncovers the molecular basis for a novel class of anion channels and provides insights into the gating and modulation of the R-type anion channel.

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Qin, L., Tang, L.-h., Xu, J.-s., Zhang, X.-h., Zhu, Y., Zhang, C.-r., Liu, X.-l., Wang, M.-h., Li, F., Sun, F., Su, M., Zhai, Y.-J., Chen, Y.-h.. 2021-09-10. Molecular basis for the R-type anion channel QUAC1 activity in guard cells. https://doi.org/10.1101/2021.09.09.459598

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