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Involvement of a tryptophan residue in the assembly of bacteriophages 80 and lambda
Abstract:
The assembly of infective particles of bacteriophages lambda and phi80 from heads and tails was found to be inhibited by l-tryptophan and some of its analogues, most notably tryptamine. Both the rate of assembly and the final yield of phage were inhibited. The amino acid l-phenylalanine had a slight inhibitory effect, whereas all other amino acids found in proteins were ineffective. Evidence was presented to show that the binding of heads to tails was the affected process in the assay for assembly of infective units. The plaque-forming ability of preassembled phage was not affected by these inhibitors. Results of three different types of experiments suggest that inhibition is due to interaction of inhibitors with the head substructure. The assembly reaction is highly dependent on pH, ionic strength, and the presence of detergents.
Insights
L-tryptophan and tryptamine inhibit bacteriophage assembly by interfering with head-tail binding. This affects phage yield but not infectivity of pre-assembled particles.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Bacteriophages are viruses that infect bacteria, with assembly being crucial for infectivity.
- Understanding bacteriophage assembly mechanisms is key to controlling viral replication and developing phage therapies.
- Specific molecular interactions governing phage assembly are not fully elucidated.
Purpose of the Study:
- To investigate the effects of amino acids and their analogues on bacteriophage lambda and phi80 assembly.
- To identify specific stages of phage assembly that are sensitive to inhibition.
- To elucidate the molecular basis of inhibition during bacteriophage particle formation.
Main Methods:
- In vitro assembly assays using purified bacteriophage heads and tails.
- Measurement of infective phage particle yield and plaque-forming ability.
- Analysis of inhibitor effects on different stages of the head-tail binding process.
Main Results:
- L-tryptophan and tryptamine significantly inhibited the assembly of infective bacteriophage particles.
- Inhibition was primarily due to interference with the binding of phage heads to phage tails.
- L-phenylalanine showed a minor inhibitory effect; other amino acids were ineffective.
Conclusions:
- The study identifies l-tryptophan and tryptamine as potent inhibitors of bacteriophage assembly.
- Inhibition occurs at the head-tail binding step, likely through interaction with the head substructure.
- Assembly conditions such as pH, ionic strength, and detergents critically influence the reaction.