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The structure of a DnaB-family replicative helicase and its interactions with primase

Abstract

Helicases are essential enzymes for DNA replication, a fundamental process in all living organisms. The DnaB family are hexameric replicative helicases that unwind duplex DNA and coordinate with RNA primase and other proteins at the replication fork in prokaryotes. Here, we report the full-length crystal structure of G40P, a DnaB family helicase. The hexamer complex reveals an unusual architectural feature and a new type of assembly mechanism. The hexamer has two tiers: a three-fold symmetric N-terminal tier and a six-fold symmetric C-terminal tier. Monomers with two different conformations, termed cis and trans, come together to provide a topological solution for the dual symmetry within a hexamer. Structure-guided mutational studies indicate an important role for the N-terminal tier in binding primase and regulating primase-mediated stimulation of helicase activity. This study provides insights into the structural and functional interplay between G40P helicase and DnaG primase.

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Figure 1: The overall features of the G40P hexameric helicase structure.
Figure 2: Two distinct monomeric structures of G40P.
Figure 3: Assembly of the G40P hexamer.
Figure 4: G40P helicase activity and helicase-primase interactions.

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Acknowledgements

We thank the staffs at Lawrence Berkeley Laboratory's Advanced Light Source beamlines 8.2.1, 8.2.2, 4.2.2 and Argonne National Laboratory's Advanced Photon Source 19id for assistance in data collection.

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Correspondence to Xiaojiang S Chen.

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Wang, G., Klein, M., Tokonzaba, E. et al. The structure of a DnaB-family replicative helicase and its interactions with primase. Nat Struct Mol Biol 15, 94–100 (2008). https://doi.org/10.1038/nsmb1356

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