Pseudomonas aeruginosa possesses two putative type I signal peptidases, LepB and PA1303, each with distinct roles in physiology and virulence.
Type I signal peptidases (SPases) cleave signal peptides from proteins during translocation across biological membranes and hence play a vital role in cellular physiology. SPase activity is also of fundamental importance to the pathogenesis of infection for many bacteria, including Pseudomonas aeruginosa, which utilizes a variety of secreted virulence factors, such as proteases and toxins. P. aeruginosa possesses two noncontiguous SPase homologues, LepB (PA0768) and PA1303, which share 43% amino acid identity. Reverse transcription (RT)-PCR showed that both proteases were expressed, while a FRET-based assay using a peptide based on the signal sequence cleavage region of the secreted LasB elastase showed that recombinant LepB and PA1303 enzymes were both active. LepB is positioned within a genetic locus that resembles the locus containing the extensively characterized SPase of E. coli and is of similar size and topology. It was also shown to be essential for viability and to have high sequence identity with SPases from other pseudomonads (≥ 78%). In contrast, PA1303, which is small for a Gram-negative SPase (20 kDa), was found to be dispensable. Mutation of PA1303 resulted in an altered protein secretion profile and increased N-butanoyl homoserine lactone production and influenced several quorum-sensing-controlled phenotypic traits, including swarming motility and the production of rhamnolipid and elastinolytic activity. The data indicate different cellular roles for these P. aeruginosa SPase paralogues; the role of PA1303 is integrated with the quorum-sensing cascade and includes the suppression of virulence factor secretion and virulence-associated phenotypes, while LepB is the primary SPase.
Centre for Immunology and Infectious Disease (CIID), Blizard Institute, Barts, and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom. r.d.waite@qmul.ac.uk
Richard D
RD
Waite
Ruth S
RS
Rose
Minnie
M
Rangarajan
Joseph
J
Aduse-Opoku
Ahmed
A
Hashim
Michael A
MA
Curtis
D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000096:biosynthesis; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D050296:Microbial Viability; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D021382:Protein Sorting Signals; D011550:Pseudomonas aeruginosa / Q000201:enzymology* / Q000378:metabolism / Q000472:pathogenicity*; D053038:Quorum Sensing; D011994:Recombinant Proteins; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000235:genetics
D001426:Bacterial Proteins; D008565:Membrane Proteins; C092312:N-butyrylhomoserine lactone; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D037521:Virulence Factors; D012697:Serine Endopeptidases; C026515:type I signal peptidase; D015107:4-Butyrolactone