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An antimicrobial peptide is produced by extracellular processing of a protein from Propionibacterium jensenii
Therese Faye1, Dag Anders Brede, Thor Langsrud
1Department of Food Science, Agricultural University of Norway, As, Norway.
Abstract:
A protease-activated antimicrobial peptide (PAMP) and its inactive precursor were purified from the culture supernatant of Propionibacterium jensenii LMG 3032 and characterized at the molecular level. PAMP is a 64-amino-acid cationic peptide of 6,383 Da with physicochemical features similar to those of bacteriocins from gram-positive bacteria. This peptide displayed bactericidal activity against several propionibacteria and lactobacilli. DNA sequencing indicated that the PAMP-encoding gene (pamA) is translated as a proprotein of 198 amino acids with an N-terminal signal peptide of 27 amino acids and that PAMP constitutes the C-terminal part of this precursor. The amino acid sequence of pro-PAMP showed no similarity to those of other known proteins. By using activity tests and mass spectrometry, we showed that PAMP was formed upon protease treatment of the precursor protein. The propionibacteria produced the PAMP precursor constitutively during growth up to a level of approximately 4 mg/liter, but the producing bacteria were unable to activate the precursor. The requirement for an external protease represents a novel strategy for generating antimicrobial peptides.
Insights
Propionibacterium jensenii produces a novel protease-activated antimicrobial peptide (PAMP) precursor. External protease activation is required, offering a new strategy for generating antimicrobial peptides against propionibacteria and lactobacilli.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Antimicrobial peptides (AMPs) are crucial components of innate immunity.
- Bacteriocins, a class of AMPs, are produced by bacteria to inhibit competitors.
- Propionibacterium jensenii is a bacterium known for its potential probiotic properties.
Purpose of the Study:
- To purify and characterize a novel antimicrobial peptide from Propionibacterium jensenii LMG 3032.
- To elucidate the molecular mechanism of antimicrobial peptide activation.
- To investigate the potential of this peptide as a therapeutic agent.
Main Methods:
- Purification of the antimicrobial peptide and its precursor from bacterial culture supernatant.
- Molecular characterization including DNA sequencing and mass spectrometry.
- Activity assays to determine the bactericidal spectrum of the peptide.
Main Results:
- A 64-amino acid cationic antimicrobial peptide (PAMP) was purified, with physicochemical properties similar to bacteriocins.
- The PAMP precursor (pro-PAMP) is translated as a 198-amino acid proprotein, with PAMP located at the C-terminus.
- PAMP is generated through protease-mediated cleavage of the pro-PAMP precursor, a process not performed by the producing bacteria.
Conclusions:
- Propionibacterium jensenii produces a PAMP precursor that requires external protease activation.
- This protease-activated mechanism represents a novel strategy for generating antimicrobial peptides.
- The characterized PAMP exhibits bactericidal activity against related propionibacteria and lactobacilli.