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Abstract: Pathogenic microorganisms have to face hostile environments while colonizing and infecting their hosts. Unfortunately, they can cope with it and have evolved a number of complex secretion systems, which direct virulence factors either at the bacterial cell surface into the environmental extracellular milieu or into the host cell cytosol. Six different classes of secretion systems have been described so far, currently identified as type I secretion system (T1SS) up to type VI secretion system (T6SS). The Gram-negative opportunistic human pathogen Pseudomonas aeruginosa possesses a broad panel of secretion systems. Five of the six secretion machines characterized in Gram-negative bacteria are at P. aeruginosa disposal, sometimes in several copies. All these machines are dedicated to the specific secretion of exoproteins, which display various activities useful for bacterial adaptation to the environment or for bacterial pathogenicity. This review will summarize the functional organization of these different secretion systems, which could constitute potential targets for therapeutic treatment of patients infected by one of the most potent nosocomial pathogens identified nowadays. [ABSTRACT FROM AUTHOR]

Abstract: In Gram-negative bacteria, most of the sec-dependent exoproteins are secreted via the type II secretion system (T2SS or secreton). In Pseudomonas aeruginosa, T2SS consists of 12 Xcp proteins (XcpA and XcpP to XcpZ) organized as a multiproteic complex within the envelope. In this study, by a co-purification approach using a His-tagged XcpZ as a bait, XcpY and XcpZ were found associated together to constitute the most stable functional unit so far isolated from the P. aeruginosa secreton. This subcomplex was also found to interact with XcpR and XcpS to form a XcpRSYZ complex which was isolated under native conditions. Another component, XcpP was not found to be associated to the complex but the results suggest that it can transiently interact with the XcpYZ subcomplex in vivo. [Copyright &y& Elsevier]

Abstract: In Gram-negative bacteria, most signal-peptide-dependent exoproteins are secreted via the type II secretion system (T2SS or secreton). In Pseudomonas aeruginosa, T2SS consists of twelve Xcp proteins (XcpA and XcpP to XcpZ) thought to be organized as a multiproteic complex within the envelope. Although well conserved, T2SS are known to be species-specific, namely for distant organisms, and this characteristic was thought to involve XcpP. To check which domain of XcpP could be involved in the species specificity, hybrid proteins were generated using protein domain swapping between P. aeruginosa XcpP and homolog proteins of either Erwinia chrysanthemi or Pseudomonas alcaligenes. The results obtained with hybrid proteins constructed by exchanging the C-terminal domains of P. aeruginosa and E. chrysanthemi suggested that XcpP interacts with XcpQ, probably via its C-terminal domain. More interestingly, the data obtained with a hybrid protein containing the C-terminal part of the P. alcaligenes XcpP homolog, showed that the wild-type C-terminal end plays a very important role in the function of the protein and is required both for a correct interaction with XcpQ and for modulating the opening of the secreton channel. [Copyright &y& Elsevier]

Identifies XcpZ domains for the assembly of Pseudomonas aeruginosa secreton. Mechanism of exoprotein transport; Structure of XcpZ and XcpY proteins; Restoration of type II secretory system in gram-negative bacteria.