title: Structural analysis of Escherichia coli ThiF.
abstract: Escherichia coli ThiF is an enzyme in the biosynthetic cascade for generating the essential cofactor thiamin pyrophosphate. In this cascade, ThiF catalyzes adenylation of the C terminus of ThiS. We report here the crystal structures of ThiF, alone and in complex with ATP. The structures provide insight into a preference for ATP during adenylation of the protein ThiS. Additionally, the structures reveal an ordered crossover loop predicted to clamp the flexible tail of ThiS into the ThiF active site during the adenylation reaction. The importance of the crossover loop for ThiF activity is highlighted by mutational analysis. Comparison of ThiF with the structural homologues MoeB, APPBP1-UBA3, and SAE1-SAE2 reveals that the ATP-binding site, including an arginine-finger, is maintained throughout evolution, and shows divergence occurring in protein substrate-binding sites and regions devoted to unique steps in the specific function of each enzyme.
authors.affiliation: Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Duda
authors.forename: Helen
authors.initials: H
authors.lastname: Walden
authors.forename: John
authors.initials: J
authors.lastname: Sfondouris
authors.forename: Brenda A
authors.initials: BA
authors.lastname: Schulman
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002384:Catalysis; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D013379:Substrate Specificity; D013831:Thiamine / Q000096:biosynthesis / Q000737:chemistry; D015032:Zinc / Q000737:chemistry / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D009711:Nucleotides; C411655:thiS protein, E coli; D000255:Adenosine Triphosphate; D009713:Nucleotidyltransferases; C411654:ThiF protein, E coli; D015032:Zinc; D013831:Thiamine