Cryo-EM Structures of Azospirillum brasilense Glutamate Synthase in Its Oligomeric Assemblies. Issue 22 (8th November 2019)

• Record Type: Journal Article
• Authors: Swuec, Paolo; Chaves-Sanjuan, Antonio; Camilloni, Carlo; Vanoni, Maria Antonietta; Bolognesi, Martino
• Is Part Of: Journal of molecular biology. Volume 431:Issue 22(2019)
• Page Start: 4523
• Page End: 4526
• Publication Date: 2019-11-08
• Subjects: GltS Azospirillum brasilense glutamate synthase -- αGltS α-subunit of GltS -- βGltS β-subunit of GltS -- rmsd root mean square deviation -- 2-OG 2-oxoglutarate; glutamate synthase -- iron/sulfur flavoprotein -- Fe/S clusters -- cryo-electron microscopy -- protein oligomeric structure; Molecular biology -- Periodicals; Biology -- Periodicals; Biochemistry -- Periodicals; Bacteriology -- Periodicals; Molecular Biology -- Periodicals; Biochemistry -- Periodicals; Biologie moléculaire -- Périodiques; Biologie -- Périodiques; Biochimie -- Périodiques; Moleculaire biologie; Biochemistry; Biology; Molecular biology; Periodicals; 572.805
• DOI: 10.1016/j.jmb.2019.08.011
• Languages: English
• ISSNs: 0022-2836

Abstract

Abstract: Bacterial NADPH-dependent glutamate synthase (GltS) is a complex iron–sulfur flavoprotein that catalyzes the reductive synthesis of two L-Glu molecules from L-Gln and 2-oxo-glutarate. GltS functional unit hosts an α-subunit (αGltS) and a β-subunit (βGltS) that assemble in different αβ oligomers in solution. Here, we present the cryo-electron microscopy structures of Azospirillum brasilense GltS in four different oligomeric states (α4 β3, α4 β4, α6 β4 and α6 β6, in the 3.5- to 4.1-Å resolution range). Our study provides a comprehensive GltS model that details the inter-protomeric assemblies and allows unequivocal location of the FAD cofactor and of two electron transfer [4Fe–4S] +1, +2 clusters within βGltS. Graphical abstract: Unlabelled Image Highlights: Cryo-EM structures of glutamate synthase α/β oligomers presented at 3.5-4.1 Å. Different α/β subunit assemblies are structurally related to the a6b6 species. First residue-resolution level structure of glutamate synthase β-subunit. The FAD site and two [4Fe-4S] +1, +2 clusters are detailed in the β-subunit core. The αβ protomer structure shows the FAD-to-FMN 50 Å full electron transfer path.