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Title: Molecular and functional characterization of type I signal peptidase from Legionella pneumophila
Authors: Lammertyn, Elke ×
Van Mellaert, Lieve
Meyen, Eva
Lebeau, Ilya
De Buck, Emmy
Anné, Jozef
Geukens, Nick #
Issue Date: May-2004
Series Title: Microbiology vol:150 issue:Pt 5 pages:1475-83
Abstract: Legionella pneumophila is a facultative intracellular Gram-negative rod-shaped bacterium that has become an important cause of both community-acquired and nosocomial pneumonia. Numerous studies concerning the unravelling of the virulence mechanism of this important pathogen have been initiated. As evidence is now accumulating for the involvement of protein secretion systems in bacterial virulence in general, the type I signal peptidase (LepB) of L. pneumophila was of particular interest. This endopeptidase plays an essential role in the processing of preproteins carrying a typical amino-terminal signal peptide, upon translocation across the cytoplasmic membrane. This paper reports the cloning and the transcriptional analysis of the L. pneumophila lepB gene encoding the type I signal peptidase (SPase). Reverse transcription PCR experiments showed clear lepB expression when L. pneumophila was grown both in culture medium, and also intracellularly in Acanthamoeba castellanii, a natural eukaryotic host of L. pneumophila. In addition, LepB was shown to be encoded by a polycistronic mRNA transcript together with two other proteins, i.e. a LepA homologue and a ribonuclease III homologue. SPase activity of the LepB protein was demonstrated by in vivo complementation analysis in a temperature-sensitive Escherichia coli lepB mutant. Protein sequence and predicted membrane topology were compared to those of leader peptidases of other Gram-negative human pathogens. Most strikingly, a strictly conserved methionine residue in the substrate binding pocket was replaced by a leucine residue, which might influence substrate recognition. Finally it was shown by in vivo experiments that L. pneumophila LepB is a target for (5S,6S)-6-[(R)-acetoxyethyl]-penem-3-carboxylate, a specific inhibitor of type I SPases.
URI: 
ISSN: 1350-0872
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Laboratory of Molecular Bacteriology (Rega Institute)
Laboratory of Virology and Chemotherapy (Rega Institute)
Academic Center for General Practice
× corresponding author
# (joint) last author

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