The Bacillus subtilis DnaD and DnaB proteins exhibit different DNA remodelling activities.
Primosomal protein cascades load the replicative helicase onto DNA. In Bacillus subtilis a putative primosomal cascade involving the DnaD-DnaB-DnaI proteins has been suggested to participate in both the DnaA and PriA-dependent loading of the replicative helicase DnaC onto the DNA. Recently we discovered that DnaD has a global remodelling DNA activity suggesting a more widespread role in bacterial nucleoid architecture. Here, we show that DnaB forms a "square-like" tetramer with a hole in the centre and suggest a model for its interaction with DNA. It has a global DNA remodelling activity that is different from that of DnaD. Whereas DnaD opens up supercoiled DNA, DnaB acts as a lateral compaction protein. The two competing activities can act together on a supercoiled plasmid forming two topologically distinct poles; one compacted with DnaB and the other open with DnaD. We propose that the primary roles of DnaB and DnaD are in bacterial nucleoid architecture control and modulation, and their effects on the initiation of DNA replication are a secondary role resulting from architectural perturbations of chromosomal DNA.
Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7, 2RD, UK.
Wenke
W
Zhang
Maria J V M
MJ
Carneiro
Ian J
IJ
Turner
Stephanie
S
Allen
Clive J
CJ
Roberts
Panos
P
Soultanas
D001412:Bacillus subtilis / Q000737:chemistry / Q000235:genetics*; D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology*; D004247:DNA / Q000378:metabolism*; D004265:DNA Helicases / Q000378:metabolism / Q000502:physiology*; D004278:DNA, Superhelical / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D053488:DnaB Helicases; D046912:Multiprotein Complexes; D009690:Nucleic Acid Conformation
D001426:Bacterial Proteins; D004278:DNA, Superhelical; D004268:DNA-Binding Proteins; C092895:DnaD protein, Bacillus subtilis; C448302:DnaI protein, Bacillus subtilis; D046912:Multiprotein Complexes; D004247:DNA; D004265:DNA Helicases; D053488:DnaB Helicases