title: Type III secretion system translocator has a molten globule conformation both in its free and chaperone-bound forms.
abstract: Type III secretion systems of Gram-negative pathogenic bacteria allow the injection of effector proteins into the cytosol of host eukaryotic cells. Crossing of the eukaryotic plasma membrane is facilitated by a translocon, an oligomeric structure made up of two bacterial proteins inserted into the host membrane during infection. In Pseudomonas aeruginosa, a major human opportunistic pathogen, these proteins are PopB and PopD. Their interactions with their common chaperone PcrH in the cytosol of the bacteria are essential for the proper function of the injection system. The interaction region between PopD and PcrH was identified using limited proteolysis, revealing that the putative PopD transmembrane fragment is buried within the PopD/PcrH complex. In addition, structural features of PopD and PcrH, either individually or within the binary complex, were characterized using spectroscopic methods and 1D NMR. Whereas PcrH possesses the characteristics of a folded protein, PopD is in a molten globule state either alone or in the PopD/PcrH complex. The molten globule state is known to enable the membrane insertion of translocation/pore-forming domains of bacterial toxins. Therefore, within the bacterial cytoplasm, PopD is preserved in a state that is favorable to secretion and insertion into cell membranes.
authors.affiliation: CEA Grenoble, DSV-iRTSV, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR5092 (CNRS, CEA, Université Joseph Fourier), Grenoble, France Institut de Biologie Structurale Jean-Pierre Ebel, UMR5075 (CNRS, CEA, Université Joseph Fourier), Grenoble, France CEA Grenoble, DSV-iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR5249 (CNRS, CEA, Université Joseph Fourier), Grenoble, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Faudry
authors.affiliation: CEA Grenoble, DSV-iRTSV, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR5092 (CNRS, CEA, Université Joseph Fourier), Grenoble, France Institut de Biologie Structurale Jean-Pierre Ebel, UMR5075 (CNRS, CEA, Université Joseph Fourier), Grenoble, France CEA Grenoble, DSV-iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR5249 (CNRS, CEA, Université Joseph Fourier), Grenoble, France.
authors.forename: Viviana
authors.initials: V
authors.lastname: Job
authors.affiliation: CEA Grenoble, DSV-iRTSV, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR5092 (CNRS, CEA, Université Joseph Fourier), Grenoble, France Institut de Biologie Structurale Jean-Pierre Ebel, UMR5075 (CNRS, CEA, Université Joseph Fourier), Grenoble, France CEA Grenoble, DSV-iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR5249 (CNRS, CEA, Université Joseph Fourier), Grenoble, France.
authors.forename: Andréa
authors.initials: A
authors.lastname: Dessen
authors.affiliation: CEA Grenoble, DSV-iRTSV, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR5092 (CNRS, CEA, Université Joseph Fourier), Grenoble, France Institut de Biologie Structurale Jean-Pierre Ebel, UMR5075 (CNRS, CEA, Université Joseph Fourier), Grenoble, France CEA Grenoble, DSV-iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR5249 (CNRS, CEA, Université Joseph Fourier), Grenoble, France.
authors.forename: Ina
authors.initials: I
authors.lastname: Attree
authors.affiliation: CEA Grenoble, DSV-iRTSV, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR5092 (CNRS, CEA, Université Joseph Fourier), Grenoble, France Institut de Biologie Structurale Jean-Pierre Ebel, UMR5075 (CNRS, CEA, Université Joseph Fourier), Grenoble, France CEA Grenoble, DSV-iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR5249 (CNRS, CEA, Université Joseph Fourier), Grenoble, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Forge
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D057927:Hydrophobic and Hydrophilic Interactions; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008968:Molecular Conformation; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D017510:Protein Folding; D012997:Solvents
chemical_list: D001426:Bacterial Proteins; D018832:Molecular Chaperones; D012997:Solvents