title: Evidence-Based Structural Model of the Staphylococcal Repressor Protein: Separation of Functions into Different Domains.
abstract: Horizontal transfer of mobile genetic elements within Staphylococci is of high biomedical significance as such elements are frequently responsible for virulence and toxic effects. Staphylococcus-encoded repressor proteins regulate the replication of these mobile genetic elements that are located within the so-called pathogenicity islands. Here, we report structural and functional characterization of one such repressor protein, namely the Stl protein encoded by the pathogenicity island SaPIbov1. We create a 3D structural model and based on this prediction, we investigate the different functionalities of truncated and point mutant constructs. Results suggest that a helix-turn-helix motif governs the interaction of the Stl protein with its cognate DNA site: point mutations within this motif drastically decrease DNA-binding ability, whereas the interaction with the Stl-binding partner protein dUTPase is unperturbed by these point mutations. The 3D model also suggested the potential independent folding of a carboxy-terminal domain. This suggestion was fully verified by independent experiments revealing that the carboxy-terminal domain does not bind to DNA but is still capable of binding to and inhibiting dUTPase. A general model is proposed, which suggests that among the several structurally different repressor superfamilies Stl-like Staphylococcal repressor proteins belong to the helix-turn-helix transcription factor group and the HTH motif is suggested to reside within N-terminal segment.
authors.affiliation: Department of Applied Biotechnology and Food Sciences, Budapest University of Technology and Economics, Budapest, 1111, Hungary; Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, 1117, Hungary.
authors.forename: Kinga
authors.initials: K
authors.lastname: Nyíri
authors.affiliation: Department of Applied Biotechnology and Food Sciences, Budapest University of Technology and Economics, Budapest, 1111, Hungary; Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, 1117, Hungary.
authors.forename: Bianka
authors.initials: B
authors.lastname: Kőhegyi
authors.affiliation: Department of Biochemistry and MTA-ELTE NAP B Neuroimmunology Research Group, Institute of Biology, Eötvös Loránd University, Budapest, 1117, Hungary.
authors.forename: András
authors.initials: A
authors.lastname: Micsonai
authors.affiliation: Department of Biochemistry and MTA-ELTE NAP B Neuroimmunology Research Group, Institute of Biology, Eötvös Loránd University, Budapest, 1117, Hungary.
authors.forename: József
authors.initials: J
authors.lastname: Kardos
authors.affiliation: Department of Applied Biotechnology and Food Sciences, Budapest University of Technology and Economics, Budapest, 1111, Hungary; Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, 1117, Hungary.
authors.forename: Beata G
authors.initials: BG
authors.lastname: Vertessy
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001435:Bacteriophages / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017354:Point Mutation / Q000235:genetics; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism*; D016415:Sequence Alignment; D013210:Staphylococcus; D040681:Structural Homology, Protein
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D004247:DNA