Origin and binding specificity of protein(s) coded for by Mu prophages.

Area of Science:

• Bacteriology
• Molecular Biology
• Genetics

Background:

• Bacteria lysogenic for bacteriophage Mu produce proteins that regulate phage gene expression.
• Understanding these regulatory proteins is crucial for controlling phage replication and lysogeny.

Purpose of the Study:

• To identify and characterize proteins from Mu-lysogenic bacteria that specifically bind Mu DNA.
• To determine the genetic basis and binding characteristics of the Mu immunity protein.

Main Methods:

• Nitrocellulose filter binding assays using crude bacterial extracts and Mu DNA.
• Competition experiments with heterologous DNA to assess binding specificity.
• Analysis of hybrid plasmids to map the gene encoding the binding activity.

Main Results:

• Proteins in crude bacterial extracts specifically retained Mu DNA on filters.
• Binding activity was directly proportional to the number of Mu prophages per genome.
• The binding activity was mapped to the left 1,000 nucleotide-pair HindIII fragment, identifying two binding sites.
• Increased immunity protein production was observed when the MucI gene was joined to the lambda early promoter.

Conclusions:

• A specific Mu DNA-binding protein, likely the immunity protein, was identified and characterized.
• The genetic locus for this binding activity was localized to a specific DNA fragment.
• Factors influencing the production levels of the immunity protein were investigated.