Phage P22 lysis genes: nucleotide sequences and functional relationships with T4 and lambda genes

Area of Science:

• Molecular Biology
• Bacteriophage Genetics

Background:

• The P22 phage lysis system is crucial for viral replication and host cell lysis.
• Understanding the genetic basis of phage lysis is essential for controlling bacterial infections and developing phage therapy.

Purpose of the Study:

• To clone and sequence the lysis genes of bacteriophage P22.
• To characterize the protein products of P22 lysis genes, specifically genes 13 and 19.
• To compare P22 lysis proteins with homologous proteins from other bacteriophages like lambda and T4.

Main Methods:

• Cloning and sequencing of wild-type and amber mutant alleles of P22 lysis genes.
• DNA sequencing to determine gene products.
• Protein purification and amino-terminal sequencing of the P22 gene 19 product.
• Construction of expression plasmids for P22, lambda, and T4 lysis genes.
• Complementation analysis to assess functional similarity.

Main Results:

• Gene 13 encodes an 11,520-Da basic hydrophobic protein with 89% amino acid homology to lambda S protein.
• Gene 19 encodes a 15,968-Da basic protein, showing limited homology to T4 lysozyme but not to lambda R or RZ proteins.
• The amino-terminal sequence of the purified P22 gene 19 protein matched the predicted DNA sequence.
• Expression plasmids for P22 gene 19, lambda genes R and RZ, and T4 gene e demonstrated functional complementation of lambda R- and P22 19- mutants.

Conclusions:

• P22 gene 13 product is homologous to lambda S protein, suggesting a conserved function in phage lysis.
• P22 gene 19 product is functionally similar to lambda R and T4 lysozyme, indicating a conserved role in cell wall degradation.
• The study provides insights into the genetic organization and functional conservation of bacteriophage lysis systems.