Cloning and expression of packaging gene 3 of Salmonella phage P22

Packaging genes 3 of Salmonella phage P22 wild type and two mutants with altered packaging properties (HT12/4 and NT1/1) have been cloned in an expression vector. By plasmid transduction, it has been shown that the amino terminus of gene 3 is not functional in DNA packaging when fused with the Escherichia coli lacZ gene. The reconstituted genes 3, however, express functional gp3. The transduction experiments also have shown that the pac signal, which is part of gene 3, is intact in all three phages. Expression of gene product gp3 has been demonstrated in the minicell system.