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The Escherichia coli DnaK chaperone machine and bacteriophage Mu late transcription
O Sand1, L Desmet, A Toussaint
1Département de Biologie Moléculaire, Université Libre de Bruxelles, Belgium.
Abstract:
Bacteriophage Mu does not grow on temperature-sensitive E. coli dnaK mutants at elevated temperatures because of a defect in late transcription. As the Mu-encoded C protein is required for activation of transcription from the phage late promoters, we attempted to determine if DnaK and its accessory proteins DnaJ and GrpE are required for synthesis of C protein or at a later step. We found that the chaperones act in Mu late transcription beyond C-protein synthesis, and that C-protein stability is decreased in the mutant hosts. This suggests that the DnaK chaperone machine may be required for the proper folding and/or multimerization of C protein.
Insights
Bacteriophage Mu requires E. coli DnaK chaperones for late transcription, acting after C protein synthesis. These chaperones are crucial for C protein stability and proper folding, enabling phage growth.
Area of Science:
- Molecular Biology
- Microbiology
- Virology
Background:
- Bacteriophage Mu growth is inhibited in temperature-sensitive E. coli dnaK mutants at higher temperatures.
- This inhibition is linked to a defect in phage late transcription.
- The bacteriophage Mu C protein is essential for activating transcription from phage late promoters.
Purpose of the Study:
- To investigate whether the E. coli DnaK, DnaJ, and GrpE chaperone proteins are required for the synthesis of the Mu C protein.
- To determine if these chaperones act at a later stage in the Mu life cycle, beyond C protein production.
Main Methods:
- Utilized temperature-sensitive E. coli dnaK mutants.
- Observed bacteriophage Mu growth and transcription patterns at elevated temperatures.
- Assessed C protein synthesis and stability in wild-type versus mutant E. coli strains.
Main Results:
- The DnaK chaperone system is not required for the initial synthesis of the Mu C protein.
- Chaperones act at a step subsequent to C protein synthesis, specifically in Mu late transcription.
- C protein stability is significantly reduced in E. coli dnaK mutant hosts.
Conclusions:
- The DnaK chaperone machine plays a critical role in bacteriophage Mu late transcription.
- This role extends beyond C protein synthesis, likely involving the proper folding and/or multimerization of the C protein.
- DnaK-dependent chaperoning is essential for maintaining C protein function and enabling phage propagation.