Differential roles of multiple signal peptidases in the virulence of Listeria monocytogenes.
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 (approximately 100-fold). Inactivation of sipZ impaired the secretion of phospholipase C (PC-PLC) and listeriolysin O (LLO), restricted intracellular multiplication and almost abolished virulence (LD(50) of 10(8.3)), 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 (LD(50) of 10(7.2)), 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.
INSERM U-570, CHU Necker-Enfants Malades, 156, rue de Vaugirard, 75730 Paris Cedex 15-France.
Claire
C
Bonnemain
Catherine
C
Raynaud
Hélène
H
Réglier-Poupet
Iharilalao
I
Dubail
Claude
C
Frehel
Marie-Annick
MA
Lety
Patrick
P
Berche
Alain
A
Charbit
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016680:Genome, Bacterial; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008089:Listeria monocytogenes / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity*; D008088:Listeriosis / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism; D037521:Virulence Factors / Q000378:metabolism
D001426:Bacterial Proteins; D007527:Isoenzymes; D008565:Membrane Proteins; D037521:Virulence Factors; D010738:Type C Phospholipases; D012697:Serine Endopeptidases; C026515:type I signal peptidase