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Structure of the Arabidopsis Glutamate Receptor-like Channel GLR3.2 Ligand-Binding Domain

Published on 02.08.2021 in Structure

Authors:

Shanti Pal Gangwar, Marriah N. Green, Erwan Michard, Alexander A. Simon, José A. Feijó, Alexander I. Sobolevsky

Our paper was featured on the Structure cover.

Glutamate receptor-like channels (GLRs) play important roles in numerous plant physiological processes. GLRs are homologous to ionotropic glutamate receptors (iGluRs) that mediate neurotransmission in vertebrates. Here we determine crystal structures of Arabidopsis thaliana GLR3.2 ligand-binding domain (LBD) in complex with glycine and methionine to 1.58- and 1.75-Å resolution, respectively. Our structures show a fold similar to that of iGluRs, but with several secondary structure elements either missing or different. The closed clamshell conformation of GLR3.2 LBD suggests that both glycine and methionine act as agonists. The mutation R133A strongly increases the constitutive activity of the channel, suggesting that the LBD mutated at the residue critical for agonist binding produces a more stable closed clamshell conformation. Furthermore, our structures explain the promiscuity of GLR activation by different amino acids, confirm evolutionary conservation of structure between GLRs and iGluRs, and predict common molecular principles of their gating mechanisms driven by bilobed clamshell-like LBDs.

This work was done in collaboration with Dr. Feijo group from University of Maryland.

The original work «Structure of the Glutamate-Like Receptor GLR3.2 ligand-binding domain» by Shanti Pal Gangwar, Marriah N. Green, Alexander I. Sobolevsky was published in BioRxiv on Dec 24, 2019.