Mechanisms of opening and closing of the bacterial replicative helicase
- City College of New York, United States
- New York Structural Biology Center, United States
- The Rockefeller University, United States
- Mahidol University, Thailand
- Harvard University, United States
Abstract
Assembly of bacterial ring-shaped hexameric replicative helicases on single-stranded (ss) DNA requires specialized loading factors. However, mechanisms implemented by these factors during opening and closing of the helicase, which enable and restrict access to an internal chamber, are not known. Here, we investigate these mechanisms in the Escherichia coli DnaB helicase•bacteriophage λ helicase loader (λP) complex. We show that five copies of λP bind at DnaB subunit interfaces and reconfigure the helicase into an open spiral conformation that is intermediate to previously observed closed ring and closed spiral forms; reconfiguration also produces openings large enough to admit ssDNA into the inner chamber. The helicase is also observed in a restrained inactive configuration that poises it to close on activating signal, and transition to the translocation state. Our findings provide insights into helicase opening, delivery to the origin and ssDNA entry, and closing in preparation for translocation.
Data availability
Cryogenic electron microscopy maps have been deposited with the EMDB under accession number EMD-7076Atomic coordinates have been deposited with the PDB under the accession code 6BBM
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Mechanisms of Opening and Closing of the Bacterial Replicative HelicaseElectron Microscopy Data Bank, EMD-7076.
Article and author information
Author details
Danaya Pakotiprapha
Funding
National Institutes of Health (GM084162)
- David Jeruzalmi
National Science Foundation (MCB 1818255)
- David Jeruzalmi
National Institutes of Health (5G12MD007603-30)
- David Jeruzalmi
Simons Foundation (SF349247)
- Edward T Eng
Agouron Institute (F00316)
- Edward T Eng
National Institutes of Health (OD019994)
- Edward T Eng
Department of Education and Training (PA200A150068)
- Jillian Chase
National Institutes of Health (P41 GM103314)
- Brian Chait
National Institutes of Health (P41 GM109824)
- Brian Chait
National Institutes of Health (F32GM128303)
- Alex J Noble
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2018, Chase et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Mechanisms of opening and closing of the bacterial replicative helicase
eLife 7:e41140.
https://doi.org/10.7554/eLife.41140
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