Involvement of a tryptophan residue in the assembly of bacteriophages 80 and lambda.

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.