Structure of a helicase-helicase loader complex reveals insights into the mechanism of bacterial primosome assembly.
Publication Type:Journal Article
Source:Nat Commun, Volume 4, p.2495 (2013)
Keywords:Adenosine Triphosphate, Bacillus, Chromatography, Gel, DNA Helicases, DNA Replication, DNA, Single-Stranded, Escherichia coli, Models, Molecular, Protein Structure, Tertiary, Static Electricity
<p>During the assembly of the bacterial loader-dependent primosome, helicase loader proteins bind to the hexameric helicase ring, deliver it onto the oriC DNA and then dissociate from the complex. Here, to provide a better understanding of this key process, we report the crystal structure of the ~570-kDa prepriming complex between the Bacillus subtilis loader protein and the Bacillus stearothermophilus helicase, as well as the helicase-binding domain of primase with a molar ratio of 6:6:3 at 7.5 Å resolution. The overall architecture of the complex exhibits a three-layered ring conformation. Moreover, the structure combined with the proposed model suggests that the shift from the 'open-ring' to the 'open-spiral' and then the 'closed-spiral' state of the helicase ring due to the binding of single-stranded DNA may be the cause of the loader release.</p>