Structure of a helicase–helicase loader complex reveals insights into the mechanism of bacterial primosome assembly

Journal Article · Thu Sep 19 04:00:00 EDT 2013 · Nature Communications

DOI:https://doi.org/10.1038/ncomms3495· OSTI ID:1095351

Liu, Bin; Eliason, William K.; Steitz, Thomas A.

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.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: NIH
• OSTI ID: 1095351
• Journal Information: Nature Communications, Journal Name: Nature Communications Vol. 4; ISSN 2041-1723
• Publisher: Nature Publishing Group
• Country of Publication: United States
• Language: ENGLISH