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Structural evidence for Arabidopsis glutathione transferase AtGSTF2 functioning as a transporter of small organic ligands

DOI: 10.1002/2211-5463.12168 DOI Help

Authors: Laziana Ahmad (University of York) , Elizabeth L. Rylott (University of York) , Neil C. Bruce (University of York) , Robert Edwards (Newcastle University) , Gideon Grogan (University of York)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Febs Open Bio

State: Published (Approved)
Published: December 2016
Diamond Proposal Number(s): 9948

Open Access Open Access

Abstract: Glutathione transferases (GSTs) are involved in many processes in plant biochemistry, with their best characterised role being the detoxification of xenobiotics through their conjugation with glutathione. GSTs have also been implicated in non-catalytic roles, including the binding and transport of small heterocyclic ligands such as indole hormones, phytoalexins and flavonoids. Although evidence for ligand binding and transport has been obtained using gene deletions and ligand binding studies on purified GSTs, there has been no structural evidence for the binding of relevant ligands in non-catalytic sites. Here we provide evidence of non-catalytic ligand binding sites in the phi class GST from the model plant Arabidopsis thaliana, AtGSTF2, revealed by X-ray crystallography. Complexes of the AtGSTF2 dimer were obtained with indole-3-aldehyde, camalexin, the flavonoid quercetrin and its non-rhamnosylated analog quercetin, at resolutions of 2.00, 2.77, 2.25 and 2.38 Å respectively. Two symmetry-equivalent binding sites (L1) were identified at the periphery of the dimer, and one more (L2) at the dimer interface. In the complexes, indole-3-aldehyde and quercetrin were found at both L1 and L2 sites, but camalexin was found only at the L1 sites and quercetin only at the L2 site. Ligand binding at each site appeared to be largely determined through hydrophobic interactions. The crystallographic studies support previous conclusions made on ligand binding in non-catalytic sites by AtGSTF2 based on isothermal calorimetry experiments (Dixon et al., Biochem. J., 2011, 438, 63-70) and suggest a mode of ligand binding in GSTs commensurate with a possible role in ligand transport.

Journal Keywords: Arabidopsis; thaliana; GST; glutathione; plant; metabolism; ligand; transport; flavonoids; structural biology; AtGSTF2

Subject Areas: Biology and Bio-materials, Chemistry


Instruments: I03-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength)

Documents:
Ahmad_et_al-2016-FEBS_Open_Bio.pdf

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