The requirement for molecular chaperones in lambda DNA replication is reduced by the mutation pi in lambda P gene, which weakens the interaction between lambda P protein and DnaB helicase.
During the initiation of lambda DNA replication, the host DnaB helicase is complexed with phage lambda P protein in order to be properly positioned near the ori lambda-lambda O initiation complex. However, the lambda P-DnaB interaction inhibits the activities of DnaB. Thus, the concerted action of bacterial heat shock proteins, DnaK, DnaJ, and GrpE, is required to activate the helicase. Wild-type phage lambda cannot grow on the E. coli dnaB, dnaK, dnaJ, and grpE mutants. However, lambda phage with a mutation pi in the lambda P gene, is able to produce progeny in these mutants as well as in the wild-type bacteria. Purified mutant lambda pi protein reveals a much lower affinity to DnaB than wild-type lambda P, and the lambda pi-DnaB complex is unstable. Also, a very low concentration of DnaK protein is sufficient to activate the helicase in a replication system based on lambda dv dsDNA. In that system, the mutant DnaK756 protein, inactive in the lambda P-dependent replication, revealed its activity in the lambda pi-dependent reaction. The lambda O-lambda P-dependent replication system based on M13 ssDNA efficiently replicates DNA in the absence of any chaperone protein, unless lambda P is substituted by the lambda pi mutant protein. Data presented in this paper explain why lambda pi phage is able to grow on wild-type and dnaK756 bacteria.
Konieczny
I
I
Department of Molecular Biology, University of Gdansk, Poland.
Marszalek
J
J
D001426:Bacterial Proteins; D017104:Bacteriophage M13 / Q000235:genetics; D010582:Bacteriophage lambda / Q000235:genetics* / Q000502:physiology; D018833:Chaperonins / Q000378:metabolism*; D003001:Cloning, Molecular; D004265:DNA Helicases / Q000378:metabolism*; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000096:biosynthesis; D004279:DNA, Viral / Q000096:biosynthesis / Q000378:metabolism; D053488:DnaB Helicases; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010957:Plasmids; D011485:Protein Binding; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
D001426:Bacterial Proteins; C024013:DNA replication complex protein, Bacteriophage lambda; D004277:DNA, Single-Stranded; D004279:DNA, Viral; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D014764:Viral Proteins; D018833:Chaperonins; C063842:dnaK protein, E coli; D004265:DNA Helicases; D053488:DnaB Helicases