title: Structural studies on the synchronization of catalytic centers in glutamate synthase.
abstract: The complex iron-sulfur flavoprotein glutamate synthase (GltS) plays a prominent role in ammonia assimilation in bacteria, yeasts, and plants. GltS catalyzes the formation of two molecules of l-glutamate from 2-oxoglutarate and l-glutamine via intramolecular channeling of ammonia. GltS has the impressive ability of synchronizing its distinct catalytic centers to avoid wasteful consumption of l-glutamine. We have determined the crystal structure of the ferredoxin-dependent GltS in several ligation and redox states. The structures reveal the crucial elements in the synchronization between the glutaminase site and the 2-iminoglutarate reduction site. The structural data combined with the catalytic properties of GltS indicate that binding of ferredoxin and 2-oxoglutarate to the FMN-binding domain of GltS induce a conformational change in the loop connecting the two catalytic centers. The rearrangement induces a shift in the catalytic elements of the amidotransferase domain, such that it becomes activated. This machinery, over a distance of more than 30 A, controls the ability of the enzyme to bind and hydrolyze the ammonia-donating substrate l-glutamine.
authors.affiliation: Department of Genetics and Microbiology, University of Pavia, via Abbiategrasso 207, 27100 Pavia, Italy.
authors.forename: Robert H H
authors.initials: RH
authors.lastname: van den Heuvel
authors.forename: Davide
authors.initials: D
authors.lastname: Ferrari
authors.forename: Roberto T
authors.initials: RT
authors.lastname: Bossi
authors.forename: Sergio
authors.initials: S
authors.lastname: Ravasio
authors.forename: Bruno
authors.initials: B
authors.lastname: Curti
authors.forename: Maria A
authors.initials: MA
authors.lastname: Vanoni
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Florencio
authors.forename: Andrea
authors.initials: A
authors.lastname: Mattevi
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000201:enzymology; D005288:Ferredoxins / Q000378:metabolism; D005970:Glutamate Synthase / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011487:Protein Conformation
chemical_list: D005288:Ferredoxins; D000594:Amino Acid Oxidoreductases; D005970:Glutamate Synthase; C042233:glutamate synthase (ferredoxin)