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

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

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24 Scopus citations

Abstract

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.

Original languageEnglish (US)
Article number2495
JournalNature communications
Volume4
DOIs
StatePublished - 2013

Bibliographical note

Funding Information:
We thank the staffs at the Advanced Photon Source beamline 24-ID and at the National Synchrotron Light Source beamline X-29/X-25 for help during data collection. This research was supported by NIH grant GM57510 to T.A.S. T.A.S. is an investigator of the Howard Hughes Medical Institute.

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