title: Role of key residues at the flavin mononucleotide (FMN):adenylyltransferase catalytic site of the bifunctional riboflavin kinase/flavin adenine dinucleotide (FAD) Synthetase from Corynebacterium ammoniagenes.
abstract: In mammals and in yeast the conversion of Riboflavin (RF) into flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) is catalysed by the sequential action of two enzymes: an ATP:riboflavin kinase (RFK) and an ATP:FMN adenylyltransferase (FMNAT). However, most prokaryotes depend on a single bifunctional enzyme, FAD synthetase (FADS), which folds into two modules: the C-terminal  associated with RFK activity and the N-terminal associated with FMNAT activity. Sequence and structural analysis suggest that the 28-HxGH-31, 123-Gx(D/N)-125 and  161-xxSSTxxR-168 motifs from FADS must be involved in ATP stabilisation for the adenylylation of FMN, as well as in FAD stabilisation for FAD phyrophosphorolysis. Mutants were produced at these motifs in the Corynebacterium ammoniagenes FADS (CaFADS). Their effects on the kinetic parameters of CaFADS activities (RFK, FMNAT and FAD pyrophosphorilase), and on substrates and product binding properties indicate that H28, H31, N125 and S164 contribute to the geometry of the catalytically competent complexes at the FMNAT-module of CaFADS.
authors.affiliation: Department of Biochemistry and Cellular and Molecular Biology, Faculty of Sciences, Institute for Biocomputation and Physics of Complex Systems (BIFI)-Joint Unit BIFI-IQFR (CSIC), University of Zaragoza, Pedro Cerbuna, 12. 50009 Zaragoza, Spain. mmedina@unizar.es.
authors.forename: Ana
authors.initials: A
authors.lastname: Serrano
authors.forename: Susana
authors.initials: S
authors.lastname: Frago
authors.forename: Adrián
authors.initials: A
authors.lastname: Velázquez-Campoy
authors.forename: Milagros
authors.initials: M
authors.lastname: Medina
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D020134:Catalytic Domain; D003352:Corynebacterium / Q000201:enzymology / Q000378:metabolism; D004789:Enzyme Activation; D004795:Enzyme Stability; D005486:Flavin Mononucleotide / Q000737:chemistry* / Q000378:metabolism*; D015870:Gene Expression; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D009154:Mutation; D009713:Nucleotidyltransferases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011485:Protein Binding; D055550:Protein Stability; D013379:Substrate Specificity; D013816:Thermodynamics
chemical_list: D005486:Flavin Mononucleotide; D000255:Adenosine Triphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C022532:riboflavin kinase; D009713:Nucleotidyltransferases; C020143:FMN adenylyltransferase