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The structural bases for agonist diversity in an Arabidopsis thaliana glutamate receptor-like channel

DOI: 10.1073/pnas.1905142117 DOI Help

Authors: Andrea Alfieri (University of Milan) , Fabrizio G. Doccula (University of Milan) , Riccardo Pederzoli (University of Milan; European Molecular Biology Laboratory, Hamburg Unit c/o DESY) , Matteo Grenzi (University of Milan) , Maria Cristina Bonza (University of Milan) , Laura Luoni (University of Milan) , Alessia Candeo (Politecnico di Milano) , Neli Romano Armada (National University of Salta) , Alberto Barbiroli (University of Milan) , Gianluca Valentini (Politecnico di Milano) , Thomas R. Schneider (European Molecular Biology Laboratory, Hamburg Unit c/o DESY) , Andrea Bassi (Politecnico di Milano) , Martino Bolognesi (University of Milan) , Marco Nardini (University of Milan) , Alex Costa (University of Milan; National Research Council of Italy (CNR))
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 117 , PAGES 752 - 760

State: Published (Approved)
Published: January 2020
Diamond Proposal Number(s): 1894

Abstract: Arabidopsis thaliana glutamate receptor-like (GLR) channels are amino acid-gated ion channels involved in physiological processes including wound signaling, stomatal regulation, and pollen tube growth. Here, fluorescence microscopy and genetics were used to confirm the central role of GLR3.3 in the amino acid-elicited cytosolic Ca2+ increase in Arabidopsis seedling roots. To elucidate the binding properties of the receptor, we biochemically reconstituted the GLR3.3 ligand-binding domain (LBD) and analyzed its selectivity profile; our binding experiments revealed the LBD preference for l-Glu but also for sulfur-containing amino acids. Furthermore, we solved the crystal structures of the GLR3.3 LBD in complex with 4 different amino acid ligands, providing a rationale for how the LBD binding site evolved to accommodate diverse amino acids, thus laying the grounds for rational mutagenesis. Last, we inspected the structures of LBDs from nonplant species and generated homology models for other GLR isoforms. Our results establish that GLR3.3 is a receptor endowed with a unique amino acid ligand profile and provide a structural framework for engineering this and other GLR isoforms to investigate their physiology.

Journal Keywords: GLR channels; X-ray crystallography; binding assay; modeling; Ca2+ signaling

Subject Areas: Biology and Bio-materials, Chemistry


Instruments: I04-Macromolecular Crystallography

Other Facilities: ESRF beamline ID29