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Following Cell-fate in E. coli After Infection by Phage Lambda
Published on: October 14, 2011
Lactococcus lactis phage operon coding for an endonuclease homologous to RuvC
E Bidnenko1, S D Ehrlich, M C Chopin
1INRA, Laboratoire de Génétique Microbienne, Jouy-en-Josas, France. elenab@biotec.jouy.inra.fr
Molecular Microbiology
|June 27, 1998
Summary
The Lactococcus lactis bacteriophage bIL66 M-operon generates DNA breaks, causing cell death in E. coli mutants. This M-operon likely encodes a structure-specific endonuclease essential for phage multiplication.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The Lactococcus lactis bacteriophage bIL66 M-operon is involved in abortive infection sensitivity.
- M-operon expression is toxic to Escherichia coli, inducing the SOS response and proving lethal to specific repair-deficient mutants.
Purpose of the Study:
- To investigate the function of the M-operon in bacteriophage bIL66.
- To elucidate the mechanism by which M-operon expression leads to cell death and DNA damage.
Main Methods:
- Utilized an inducible expression system in E. coli.
- Performed genetic and physical analysis of M-operon derivatives.
- Employed site-specific mutagenesis to study protein function.
Main Results:
- M-operon proteins induce random chromosomal double-stranded breaks (DSBs) in E. coli.
- DSBs are substrates for ExoV-mediated DNA degradation and occur in plasmids.
- Two open reading frames (ORFs), orf2 and orf3, are necessary for nucleolytic activity, with orf3 showing homology to RuvC resolvase.
Conclusions:
- The M-operon encodes a structure-specific endonuclease (M-nuclease) that targets branched DNA structures.
- A conserved glutamic acid residue (Glu-67) in ORF3 is crucial for M-nuclease activity.
- This M-nuclease is proposed to be essential for bacteriophage multiplication.
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