title: Packaging and maturation of DNA of bacteriophage T7 in vitro.
abstract: We have developed an in vitro complementation assay to demonstrate packaging and maturation of DNA of phage T7. Cells of Escherichia coli B infected with an appropriate T7 amber mutant are concentrated 200-fold and lysed by freezing and thawing. Two extracts from cells infected with different amber mutants are mixed and incubated at 30 degrees . Positive complementation results in a 100-fold increase in phage titer. Using this assay we have demonstrated the packaging of phage DNA from an extract that contains no phage heads (gene 9(-), 10(-)), within head structures present in an extract that contains no phage DNA (gene 5(-)). We have also demonstrated an activity in extracts that contain no phage DNA or heads (gene 5(-), 9(-), 10(-)), which complements gene 19(-)-infected cells. We have proven that this activity is due to the gene-19 product by showing that the activity is temperature-sensitive if the extract is made from cells infected with a mutant having a temperature-sensitive mutation in gene 19. This assay should be useful in elucidating the mechanism of packaging and maturation of DNA of phage T7.
mesh_terms: D002474:Cell-Free System; D002874:Chromosome Mapping; D003090:Coliphages / Q000378:metabolism*; D004279:DNA, Viral / Q000378:metabolism*; D005796:Genes; D009024:Morphogenesis; D009154:Mutation; D014176:Protein Biosynthesis; D013696:Temperature; D014764:Viral Proteins / Q000096:biosynthesis; D014779:Virus Replication
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins