Structural insights into toxr, a virulence regulator in vibrio cholerae

• Autores: Mireia Muriel Masanes
• Directores de la Tesis: Miquel Coll Capella (dir. tes.), Albert Canals Parera (codir. tes.)
• Lectura: En la Universitat de Barcelona ( España ) en 2020
• Idioma: español
• Tribunal Calificador de la Tesis: Miquel Pons Vallès (presid.), Maria Solà Vilarrubias (secret.), Gloria del Solar Dongil (voc.)
• Programa de doctorado: Programa de Doctorado en Biotecnología por la Universidad de Barcelona
• Materias:
  • Física
    • Electromagnetismo
      • Rayos x
    • Física del estado sólido
      • Cristalografía
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• Resumen

  • ABSTRACT The toxR gene from Vibrio cholerae encodes a transmembrane protein, which has been shown to act as a coactivator of the toxT promoter, leading to the cholera virulence cascade, and as a direct regulator of two genes encoding major outer membrane porins, OmpU and OmpT.

    The periplasmic domain of ToxR does not show any significant sequence homology with other known proteins and its function remains unclear, although some evidences suggest that it plays an important role in regulating the transcription of virulence genes by sensing different environmental signals. Available information on the cytoplasmic DNA-binding domain (DBD) bound to toxT promoter describes three essential ToxRDBD structural elements: the recognition helix, the wing and a secondary wing. In this work, high quality samples suitable for structural determination by X-ray crystallography of ToxRDBD bound to ompU promoter were obtained and characterized. In the asymmetric unit, four ToxRDBD monomers bind the -47 to -30 region, which peculiarly contains a mirror repeat pattern. Two of the monomers bind with the wing element facing the upstream end of the promoter, while the other two are oriented in the opposite direction; showing the high versatility of ToxR protein to bind in different senses, even in the same promoter. After comparing the ToxRDBD complexes bound to toxT and ompU, we conclude that ToxR binding is more DNA conformation-specific than sequencespecific and that ToxR is a highly versatile transcription factor with several, slightly-different binding capabilities. Finally, we propose a model along with RNA polymerase holoenzyme interacting with the - 35 region of ompU promoter.

    Keywords ToxR protein, periplasmic domain; DNA binding domain; ompU promoter; mirror repeat; RNA polymerase; X-ray crystallography; Vibrio cholerae; Cholera disease.