title: Structure-function studies on the complex iron-sulfur flavoprotein glutamate synthase: the key enzyme of ammonia assimilation.
abstract: Glutamate synthases are complex iron-sulfur flavoproteins that participate in the essential ammonia assimilation pathway in microorganisms and plants. The recent determination of the 3-dimensional structures of the alpha subunit of the NADPH-dependent glutamate synthase form and of the ferredoxin-dependent enzyme of Synechocystis sp. PCC 6803 provides a framework for the interpretation of the functional properties of these enzymes, and highlights protein segments most likely involved in control and coordination of the partial catalytic activities of glutamate synthases, which take place at sites distant from each other in space. In this review, we focus on the current knowledge on structure-function relationships in glutamate synthases, and we discuss open questions on the mechanisms of control of the enzyme reaction and of electron transfer among the enzyme flavin cofactors and iron-sulfur clusters.
authors.affiliation: Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Via Celoria 26, Milan 20131, Italy. maria.vanoni@unimi.it
authors.forename: Maria A
authors.initials: MA
authors.lastname: Vanoni
authors.forename: Laura
authors.initials: L
authors.lastname: Dossena
authors.forename: Robert H H
authors.initials: RH
authors.lastname: van den Heuvel
authors.forename: Bruno
authors.initials: B
authors.lastname: Curti
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D000641:Ammonia / Q000378:metabolism*; D001693:Biological Transport, Active; D002384:Catalysis; D000458:Cyanobacteria / Q000201:enzymology*; D005970:Glutamate Synthase / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D021122:Protein Subunits; D013329:Structure-Activity Relationship
chemical_list: D021122:Protein Subunits; D000641:Ammonia; D000594:Amino Acid Oxidoreductases; D005970:Glutamate Synthase; C042233:glutamate synthase (ferredoxin)