title: Mutational analysis and homology modelling of SyrC, the aminoacyltransferase in the biosynthesis of syringomycin.
abstract: SyrC, a component of the multienzyme system of syringomycin biosynthesis, has been shown to shuttle Thr/4-Cl-Thr between the thiolation domains SyrB1-T1 and SyrE-T8,9 by transiently linking it to Cys224 in the enzyme active site. We present data on the structure-function relationship in vivo of this protein and an in silico model of its three-dimensional structure. The biosynthetic activity of SyrC was not influenced when either Asp348 or His376 that together with Cys224 form a putative catalytic triad, were replaced with Ala, but it was abolished by the exchange Cys224 with Ser. The presence of the FLAG peptide on either the N- or C-terminus of the protein did not affect activity, whereas the deletion of the first 16 amino acids at the N-terminus or the insertion of Maltose Binding Protein abolished the production of syringomycin. We present the model of the three-dimensional structure of SyrC suggesting a homodimeric structure for the protein and biochemical data that are supportive of this model.
authors.affiliation: Department of Biochemical Sciences A. Rossi Fanelli, University of Rome La Sapienza, P.le A. Moro, 5, 00185 Rome, Italy.
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Fullone
authors.forename: Alessandro
authors.initials: A
authors.lastname: Paiardini
authors.forename: Dennis C
authors.initials: DC
authors.lastname: Gross
authors.forename: Shi-En
authors.initials: SE
authors.lastname: Lu
authors.forename: Alberto
authors.initials: A
authors.lastname: Fiore
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Grgurina
mesh_terms: D000595:Amino Acid Sequence; D019881:Aminoacyltransferases / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics; D019281:Dimerization; D058619:Maltose-Binding Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009842:Oligopeptides; D010453:Peptide Synthases / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D010455:Peptides / Q000235:genetics; D011487:Protein Conformation; D044224:Pseudomonas syringae / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D058619:Maltose-Binding Proteins; D009842:Oligopeptides; D010455:Peptides; D011993:Recombinant Fusion Proteins; C032677:syringomycin; C085706:FLAG peptide; D019881:Aminoacyltransferases; D010453:Peptide Synthases; C094582:SyrC protein, Pseudomonas syringae