Conformational dynamics of a transposition repressor in modulating DNA binding

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• The bacteriophage Mu repressor protein is crucial for maintaining lysogeny.
• It functions by binding to operator DNA and inhibiting transposition.
• N-terminal domains are known for DNA binding, while C-terminal mutations can be suppressed by truncations.

Purpose of the Study:

• To investigate the role of the C-terminal tail in the DNA binding of the bacteriophage Mu repressor.
• To understand the conformational changes and interactions of the repressor during DNA binding.

Main Methods:

• Fluorescent probe attachment to the C terminus to analyze its environment and movement.
• Monitoring tryptophan fluorescence quenching to assess proximity between C terminus and DNA-binding domain.
• Trypsin digestion assays to identify hypersensitive sites and assess protein stability.

Main Results:

• The C-terminal tail resides in a hydrophobic environment near the DNA-binding domain.
• DNA interaction causes the tail to move away from the DNA-binding domain.
• The tail's presence creates a trypsin-sensitive site in the DNA-binding domain, which is relieved by DNA binding.

Conclusions:

• The C-terminal tail of the bacteriophage Mu repressor sterically hinders DNA binding.
• Conformational changes involving tail movement are essential for repression establishment and cooperative DNA binding.
• These findings shed light on the dynamic regulation of bacteriophage DNA-protein interactions.