title: Influence of deletions within domain II of exotoxin A on its extracellular secretion from Pseudomonas aeruginosa.
abstract: Pseudomonas aeruginosa is a gram-negative bacterium that secretes many proteins into the extracellular medium via the Xcp machinery. This pathway, conserved in gram-negative bacteria, is called the type II pathway. The exoproteins contain information in their amino acid sequence to allow targeting to their secretion machinery. This information may be present within a conformational motif. The nature of this signal has been examined for P. aeruginosa exotoxin A (PE). Previous studies failed to identify a common minimal motif required for Xcp-dependent recognition and secretion of PE. One study identified a motif at the N terminus of the protein, whereas another one found additional information at the C terminus. In this study, we assess the role of the central PE domain II composed of six alpha-helices (A to F). The secretion behavior of PE derivatives, individually deleted for each helix, was analyzed. Helix E deletion has a drastic effect on secretion of PE, which accumulates within the periplasm. The conformational rearrangement induced in this variant is predicted from the three-dimensional PE structure, and the molecular modification is confirmed by gel filtration experiments. Helix E is in the core of the molecule and creates close contact with other domains (I and III). Deletion of the surface-exposed helix F has no effect on secretion, indicating that no secretion information is contained in this helix. Finally, we concluded that disruption of a structured domain II yields an extended form of the molecule and prevents formation of the conformational secretion motif.
authors.affiliation: Laboratoire d'Ingéniérie des Systèmes Macromoléculaires, UPR9027, France.
authors.forename: R
authors.initials: R
authors.lastname: Voulhoux
authors.forename: M P
authors.initials: MP
authors.lastname: Taupiac
authors.forename: M
authors.initials: M
authors.lastname: Czjzek
authors.forename: B
authors.initials: B
authors.lastname: Beaumelle
authors.forename: A
authors.initials: A
authors.lastname: Filloux
mesh_terms: D036002:ADP Ribose Transferases; D001426:Bacterial Proteins / Q000378:metabolism; D001427:Bacterial Toxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005098:Exotoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D016254:Mutagenesis, Insertional; D009154:Mutation; D019897:Periplasm / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D017384:Sequence Deletion; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D005098:Exotoxins; D011065:Poly(ADP-ribose) Polymerases; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A