9TZF

Vibrio cholerae DnaB-DciA open ring complex

Summary for 9TZF

• Entry DOI: 10.2210/pdb9tzf/pdb
• EMDB information: 56467
• Descriptor: Replicative DNA helicase, DUF721 domain-containing protein, ADENOSINE-5'-DIPHOSPHATE, ... (4 entities in total)
• Functional Keywords: dna replication initiation, dnab, replicative helicase, helicase loader, dcia, vibrio cholerae, replication
• Biological source: Vibrio cholerae O1 biovar El Tor str. N16961; More
• Total number of polymer chains: 9
• Total formula weight: 368084.60

Authors

Araujo-Bazan, L.,Arias-Palomo, E. (deposition date: 2026-01-22, release date: 2026-11-04)

Primary citation

Araujo-Bazan, L.,Arias-Palomo, E.
Structural basis of DnaB ring opening by the ancestral helicase loader DciA.
Nucleic Acids Res., 54:-, 2026

PubMed 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.

PubMed: 42927770
DOI: 10.1093/nar/gkag977

Experimental method

ELECTRON MICROSCOPY (3.5 Å)