Mechanisms of opening and closing of the bacterial replicative helicase

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. Her...

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Bibliographic Details
Published in:	eLife Vol. 7
Main Authors:	Chase, Jillian, Catalano, Andrew, Noble, Alex J, Eng, Edward T, Olinares, Paul Db, Molloy, Kelly, Pakotiprapha, Danaya, Samuels, Martin, Chait, Brian, des Georges, Amedee, Jeruzalmi, David
Format:	Journal Article
Language:	English
Published:	England eLife Sciences Publications Ltd 24-12-2018 eLife Sciences Publications, Ltd
Subjects:	Bacteria Bacteriophage lambda - enzymology Biochemistry Biochemistry and Chemical Biology Biology Chromosomes Conformation Cryoelectron Microscopy cryogenic electron microscopy Deoxyribonucleic acid DNA DNA helicase DNA Replication DNA, Single-Stranded - metabolism DnaB helicase DnaB Helicases - chemistry DnaB Helicases - metabolism DnaB replicative helicase E coli Escherichia coli - enzymology helicase loader Interfaces Laboratories Mass spectrometry Models, Molecular Peptides Plasmids Protein Binding Protein Conformation Proteins replication initiation Scientific imaging Single-stranded DNA structural biology Structural Biology and Molecular Biophysics Viral Proteins - chemistry Viral Proteins - metabolism New York United States > US DNA replication DnaB replicative helicase chemical biology helicase loader biochemistry structural biology molecular biophysics E. coli cryogenic electron microscopy replication initiation
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Summary:	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 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.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	2050-084X 2050-084X
DOI:	10.7554/elife.41140