title: Characterization and purification of a phage phi 29-encoded DNA polymerase required for the initiation of replication.
abstract: The phage phi 29 protein p2, required for the formation of the protein p3-dAMP initiation complex, has been purified from Escherichia coli cells harboring a gene 2-containing recombinant plasmid. The purified protein p2, of molecular weight 68,000, had a specific DNA polymerase activity that elongated the p3-dAMP initiation complex when phi 29 DNA-protein p3 was used as template. In addition, the purified protein p2 was active in catalyzing the initiation reaction when complemented with phi 29 mutant sus2-infected Bacillus subtilis or plasmid-containing E. coli extracts providing protein p3, in the presence of phi 29 DNA-protein p3 as template. However, when purified protein p3 was used in the complementation assay, a very low amount of initiation complex was formed; addition of extracts from uninfected B. subtilis or E. coli strongly stimulated the initiation reaction, indicating that, in addition to proteins p2 and p3 and the phi 29 DNA-protein p3 template, some host factor(s) is required for the formation of the p3-dAMP initiation complex. The results show that phage phi 29 encodes a DNA polymerase that is required at the initiation step of protein-primed DNA synthesis.
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics; D001435:Bacteriophages / Q000201:enzymology* / Q000235:genetics; D004261:DNA Replication; D004279:DNA, Viral / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005796:Genes; D005814:Genes, Viral; D007700:Kinetics; D008970:Molecular Weight; D013698:Templates, Genetic
chemical_list: D004279:DNA, Viral; D004259:DNA-Directed DNA Polymerase