title: Crystallographic snapshots of iterative substrate translocations during nicotianamine synthesis in Archaea.
abstract: Nicotianamine (NA), a small molecule ubiquitous in plants, is an important divalent metal chelator and the main precursor of phytosiderophores. Nicotianamine synthase (NAS) is the enzyme catalyzing NA synthesis by the condensation of three aminopropyl moieties of S-adenosylmethionine (SAM) and the cyclization of one of them to form an azetidine ring. Here we report five crystal structures of an archaeal NAS from Methanothermobacter thermautotrophicus, either free or in complex with its product(s) and substrate(s). These structures reveal a two-domains fold arrangement of MtNAS, a small molecule related to NA (named here thermoNicotianamine or tNA), and an original mechanism of synthesis in a buried reaction chamber. This reaction chamber is open to the solvent through a small inlet, and a single active site allows the selective entrance of only one substrate at a time that is then processed and translocated stepwise.
authors.affiliation: Laboratoire de Bioénergétique Cellulaire and Laboratoire des Interactions Protéine Métal, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institute of Environmental Biology and Biotechnology, Saint-Paul-lez-Durance, F-13108, France.
authors.forename: Cyril
authors.initials: C
authors.lastname: Dreyfus
authors.forename: David
authors.initials: D
authors.lastname: Lemaire
authors.forename: Stéphane
authors.initials: S
authors.lastname: Mari
authors.forename: David
authors.initials: D
authors.lastname: Pignol
authors.forename: Pascal
authors.initials: P
authors.lastname: Arnoux
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001383:Azetidinecarboxylic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D002384:Catalysis; D018360:Crystallography, X-Ray; D003500:Cyclization; D006860:Hydrogen Bonding; D013058:Mass Spectrometry; D017013:Methanobacteriaceae / Q000201:enzymology* / Q000235:genetics; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D019843:Archaeal Proteins; C082893:nicotianamine; D001383:Azetidinecarboxylic Acid; D012436:S-Adenosylmethionine; D019883:Alkyl and Aryl Transferases; C118230:nicotianamine synthase