Structural basis of DnaB ring opening by the ancestral helicase loader DciA
- 1Centro de Investigaciones Biológicas Margarita Salas, CSIC , 28040 Madrid ,
Abstract
Ring-shaped helicases must be opened and loaded onto DNA to initiate genome replication. In bacteria, most species lack canonical AAA+ helicase loaders and instead rely on DciA, an evolutionarily conserved, ATP-independent factor whose mechanism has remained unclear. Here we define how DciA remodels the bacterial replicative helicase DnaB. A 3.5 Å cryo-EM structure reveals a DnaB6·DciA3 complex in which DciA binds the periphery of the helicase and stabilizes a right-handed open-helical conformation with a single cracked interface. Three DciA molecules dock onto alternate linker-helix/docking-helix modules, while one N-terminal domain (NTD) engages the cracked interface, occupying the pocket vacated by the displaced linker helix and acting as a wedge to promote ring opening. Functional analyses reveal how DciA couples ATPase suppression with efficient helicase loading through coordinated actions of its NTDs and C-terminal domains. Together, these findings define a minimal, ATP-independent mechanism for helicase loading and show how an ancestral loader remodels DnaB to overcome a fundamental topological barrier.
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BibTeX
@article{araujobazan2026structural,
title = {{Structural basis of DnaB ring opening by the ancestral helicase loader DciA}},
author = {Lidia Araújo-Bazán and Ernesto Arias-Palomo},
journal = {Nucleic Acids Research},
year = {2026},
month = oct,
doi = {10.1093/nar/gkag977},
url = {https://academic.oup.com/nar/article/doi/10.1093/nar/gkag977/8959889},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Structural basis of DnaB ring opening by the ancestral helicase loader DciA
AU - Lidia Araújo-Bazán
AU - Ernesto Arias-Palomo
PY - 2026
DA - 2026/10/01
JO - Nucleic Acids Research
DO - 10.1093/nar/gkag977
UR - https://academic.oup.com/nar/article/doi/10.1093/nar/gkag977/8959889
AB - Ring-shaped helicases must be opened and loaded onto DNA to initiate genome replication. In bacteria, most species lack canonical AAA+ helicase loaders and instead rely on DciA, an evolutionarily conserved, ATP-independent factor whose mechanism has remained unclear. Here we define how DciA remodels the bacterial replicative helicase DnaB. A 3.5 Å cryo-EM structure reveals a DnaB6·DciA3 complex in which DciA binds the periphery of the helicase and stabilizes a right-handed open-helical conformation with a single cracked interface. Three DciA molecules dock onto alternate linker-helix/docking-helix modules, while one N-terminal domain (NTD) engages the cracked interface, occupying the pocket vacated by the displaced linker helix and acting as a wedge to promote ring opening. Functional analyses reveal how DciA couples ATPase suppression with efficient helicase loading through coordinated actions of its NTDs and C-terminal domains. Together, these findings define a minimal, ATP-independent mechanism for helicase loading and show how an ancestral loader remodels DnaB to overcome a fundamental topological barrier.
SN - 0305-1048
SN - 1362-4962
ER -