title: Oligomeric state in the crystal structure of modular FAD synthetase provides insights into its sequential catalysis in prokaryotes.
abstract: The crystal structure of the modular flavin adenine dinucleotide (FAD) synthetase from Corynebacterium ammoniagenes has been solved at 1.95 A resolution. The structure of C. ammoniagenes FAD synthetase presents two catalytic modules-a C-terminus with ATP-riboflavin kinase activity and an N-terminus with ATP-flavin mononucleotide (FMN) adenylyltransferase activity-that are responsible for the synthesis of FAD from riboflavin in two sequential steps. In the monomeric structure, the active sites from both modules are placed 40 A away, preventing the direct transfer of the product from the first reaction (FMN) to the second catalytic site, where it acts as substrate. Crystallographic and biophysical studies revealed a hexameric assembly formed by the interaction of two trimers. Each trimer presents a head-tail configuration, with FMN adenylyltransferase and riboflavin kinase modules from different protomers approaching the active sites and allowing the direct transfer of FMN. Experimental results provide molecular-level evidences of the mechanism of the synthesis of FMN and FAD in prokaryotes in which the oligomeric state could be involved in the regulation of the catalytic efficiency of the modular enzyme.
authors.affiliation: Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Herguedas
authors.forename: Marta
authors.initials: M
authors.lastname: Martínez-Júlvez
authors.forename: Susana
authors.initials: S
authors.lastname: Frago
authors.forename: Milagros
authors.initials: M
authors.lastname: Medina
authors.forename: Juan A
authors.initials: JA
authors.lastname: Hermoso
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D020134:Catalytic Domain; D003352:Corynebacterium / Q000201:enzymology*; D018360:Crystallography, X-Ray; D005486:Flavin Mononucleotide / Q000737:chemistry / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009713:Nucleotidyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011387:Prokaryotic Cells / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: D005182:Flavin-Adenine Dinucleotide; D005486:Flavin Mononucleotide; D000255:Adenosine Triphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C022532:riboflavin kinase; D009713:Nucleotidyltransferases; C020143:FMN adenylyltransferase