title: The interaction of bacteriophage P2 B protein with Escherichia coli DnaB helicase.
abstract: Bacteriophage P2 requires several host proteins for lytic replication, including helicase DnaB but not the helicase loader, DnaC. Some genetic studies have suggested that the loading is done by a phage-encoded protein, P2 B. However, a P2 minichromosome containing only the P2 initiator gene A and a marker gene can be established as a plasmid without requiring the P2 B gene. Here we demonstrate that P2 B associates with DnaB. This was done by using the yeast two-hybrid system in vivo and was confirmed in vitro, where (35)S-labeled P2 B bound specifically to DnaB adsorbed to Q Sepharose beads and monoclonal antibodies directed against the His-tagged P2 B protein were shown to coprecipitate the DnaB protein. Finally, P2 B was shown to stabilize the opening of a reporter origin, a reaction that is facilitated by the inactivation of DnaB. In this respect, P2 B was comparable to lambda P protein, which is known to be capable of binding and inactivating the helicase while acting as a helicase loader. Even though P2 B has little similarity to other known or predicted helicase loaders, we suggest that P2 B is required for efficient loading of DnaB and that this role, although dispensable for P2 plasmid replication, becomes essential for P2 lytic replication.
authors.affiliation: Department of Genetics, Stockholm University, S-10691 Stockholm, Sweden.
authors.forename: R
authors.initials: R
authors.lastname: Odegrip
authors.forename: S
authors.initials: S
authors.lastname: Schoen
authors.forename: E
authors.initials: E
authors.lastname: Haggård-Ljungquist
authors.forename: K
authors.initials: K
authors.lastname: Park
authors.forename: D K
authors.initials: DK
authors.lastname: Chattoraj
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D017901:Bacteriophage P2 / Q000378:metabolism*; D003001:Cloning, Molecular; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D053488:DnaB Helicases; D004926:Escherichia coli / Q000201:enzymology*; D008969:Molecular Sequence Data; D010957:Plasmids; D012441:Saccharomyces cerevisiae; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C407903:B protein, Enterobacteria phage P2; D001426:Bacterial Proteins; D014764:Viral Proteins; D004265:DNA Helicases; D053488:DnaB Helicases