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  • 1
    Electronic Resource
    Electronic Resource
    Identification of a PEST-like motif in listeriolysin O required for phagosomal escape and for virulence in Listeria monocytogenes (2001)
    Oxford, UK : Blackwell Science, Ltd
    Molecular microbiology 39 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The hly-encoded listeriolysin O (LLO) is a major virulence factor secreted by the intracellular pathogen Listeria monocytogenes, which plays a crucial role in the escape of bacteria from the phagosomal compartment. Here, we identify a putative PEST sequence close to the N-terminus of LLO and focus on the role of this motif in the biological activities of LLO. Two LLO variants were constructed: a deletion mutant protein, lacking the 19 residues comprising this sequence (residues 32–50), and a recombinant protein of wild-type size, in which all the P, E, S or T residues within this motif have been substituted. The two mutant proteins were fully haemolytic and were secreted in culture supernatants of L. monocytogenes in quantities comparable with that of the wild-type protein. Strikingly, both mutants failed to restore virulence to a hly-negative strain in vivo. In vitro assays showed that L. monocytogenes expressing the LLO deletion mutant was strongly impaired in its ability to escape from the phagosomal vacuole and, subsequently, to divide in the cytosol of infected cells. This work reveals for the first time that the N-terminal portion of LLO plays an important role in the development of the infectious process of L. monocytogenes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2001.02281.x
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  • 2
    Electronic Resource
    Electronic Resource
    Critical role of the N-terminal residues of listeriolysin O in phagosomal escape and virulence of Listeria monocytogenes (2002)
    Oxford, UK : Blackwell Science, Ltd
    Molecular microbiology 46 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A putative PEST sequence was recently identified close to the N-terminus of listeriolysin O (LLO), a major virulence factor secreted by the pathogenic Listeria monocytogenes. The deletion of this motif did not affect the secretion and haemolytic activity of LLO, but abolished bacterial virulence. Here, we first tested whether the replacement of the PEST motif of LLO by two different sequences, with either a very high or no PEST score, would affect phagosomal escape, protein stability and, ultimately, the virulence of L. monocytogenes. Then, we constructed LLO mutants with an intact PEST sequence but carrying mutations on either side, or on both sides, of the PEST motif. The properties of these mutants prompted us to construct three LLO mutants carrying single amino acid substitutions in the distal portion of the PEST region (P49A, K50A and P52A; preprotein numbering). Our data demonstrate that the susceptibility of LLO to intracellular proteolytic degradation is not related to the presence of a high PEST score sequence and that the insertion of two residues immediately downstream of the intact PEST sequence is sufficient to impair phagosomal escape and abolish bacterial virulence. Furthermore, we show that single amino acid substitutions in the distal portion of the PEST motif are sufficient to attenuate bacterial ­virulence significantly, unravelling the critical role of this region of LLO in the pathogenesis of L. ­monocytogenes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03176.x
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  • 3
    Electronic Resource
    Electronic Resource
    Differential roles of multiple signal peptidases in the virulence of Listeria monocytogenes (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 51 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Most bacteria contain one type I signal peptidase (Spase I) for cleavage of signal peptides from exported and secreted proteins. Here, we identified a locus encoding three contiguous Spase I genes in the genome of Listeria monocytogenes. The deduced Sip proteins (denoted SipX, SipY and SipZ) are significantly similar to SipS and SipT, the major SPase I proteins of Bacillus subtilis (38% to 44% peptidic identity). We studied the role of these multiple signal peptidases in bacterial pathogenicity by constructing a series of single- and double-chromosomal knock-out mutants. Inactivation of sipX did not affect intracellular multiplication of L. monocytogenes but significantly reduced bacterial virulence (∼ 100-fold). Inactivation of sipZ impaired the secretion of phospholipase C (PC-PLC) and listeriolysin O (LLO), restricted intracellular multiplication and almost abolished virulence (LD50 of 108.3), inactivation of sipY had no detectable effects. Most importantly, a mutant expressing only SipX was impaired in intracellular survival and strongly attenuated in the mouse (LD50 of 107.2), whereas, a mutant expressing only SipZ behaved like wild-type EGD in all the assays performed. The data establish that SipX and SipZ perform distinct functions in bacterial pathogenicity and that SipZ is the major Spase I of L. monocytogenes. This work constitutes the first report on the differential role of multiple Spases I in a pathogenic bacterium and suggests a possible post-translational control mechanism of virulence factors expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.03916.x
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