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Journal of Bacteriology, July 2000, p. 4051-4058, Vol. 182, No. 14
Laboratoire d'Ingéniérie des
Systèmes Macromoléculaires,
UPR9027,1 and Laboratoire
d'Architecture et Fonction des Macromolécules Biologiques,
UPR9039,3 IBSM/CNRS, 13402 Marseille Cedex 20, and UMR 5539 CNRS, Département Biologie-Santé, Case
107, Université Montpellier II, 34905 Montpellier Cedex
05,2 France
Received 9 February 2000/Accepted 21 April 2000
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
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Influence of Deletions within Domain II of Exotoxin
A on Its Extracellular Secretion from Pseudomonas
aeruginosa
-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.
*
Corresponding author. Mailing address: Laboratoire
d'Ingéniérie des Systèmes Macromoléculaires,
UPR9027, IBSM/CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France. Phone: (33) (0)491164127. Fax: (33) (0)491712124. E-mail:
filloux{at}ibsm.cnrs-mrs.fr.
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