title: A new member of the ribbon-helix-helix transcription factor superfamily from the plant pathogen Xanthomonas axonopodis pv.citri.
abstract: XACb0070 is an uncharacterized protein coded by the two large plasmids isolated from Xanthomonas axonopodis pv. citri, the agent of citrus canker and responsible for important economical losses in citrus world production. XACb0070 presents sequence homology only with other hypothetical proteins belonging to plant pathogens, none of which have their structure determined. The NMR-derived solution structure reveals this protein is a homodimer in which each monomer presents two domains with different structural and dynamic properties: a folded N-terminal domain with beta alpha alpha topology which mediates dimerization and a long disordered C-terminal tail. The folded domain shows high structural similarity to the ribbon-helix-helix transcriptional repressors, a family of DNA-binding proteins of conserved 3D fold but low sequence homology: indeed XACb0070 binds DNA. Primary sequence and fold comparison of XACb0070 with other proteins of the ribbon-helix-helix family together with examination of the genes in the vicinity of xacb0070 suggest the protein might be the component of a toxin-antitoxin system.
authors.affiliation: Department of Chemical Science and Technology, University of Rome Tor Vergata, Rome 00133, Italy.
authors.forename: Mariana
authors.initials: M
authors.lastname: Gallo
authors.forename: Elena
authors.initials: E
authors.lastname: Ferrari
authors.forename: Tommaso
authors.initials: T
authors.lastname: Eliseo
authors.forename: Irene
authors.initials: I
authors.lastname: Amata
authors.forename: Thelma A
authors.initials: TA
authors.lastname: Pertinhez
authors.forename: Angela M
authors.initials: AM
authors.lastname: Katsuyama
authors.forename: Maurizio
authors.initials: M
authors.lastname: Paci
authors.forename: Chuck S
authors.initials: CS
authors.lastname: Farah
authors.forename: Alberto
authors.initials: A
authors.lastname: Spisni
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Cicero
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002957:Citrus / Q000382:microbiology*; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010957:Plasmids / Q000235:genetics; D011487:Protein Conformation; D017422:Sequence Analysis, DNA; D013050:Spectrometry, Fluorescence; D014157:Transcription Factors / Q000235:genetics*; D053532:Xanthomonas axonopodis / Q000235:genetics*
chemical_list: D014157:Transcription Factors