DnaB-DnaG complex

GO:1990156 · Other · Multiprotein complex · Proposed

A protein complex containing homohexameric DnaB helicase, and DnaG (a primase). Facilitates the unwinding of double-stranded DNA and the synthesis of RNA primer sequences during DNA replication and repair in Prokaryotes. [GO:1990156]

Synonyms: DnaB-DnaG primosome complex

Part of: core primosome complex (GO:1990098)

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
DnaB helicase	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	dnaB	6 copies per DnaB homohexamer	UNKNOWN	Homohexameric DNA helicase constituent of the primase-bound DnaB-DnaG complex. `GO:1990156` GO:1990156 defines the DnaB-DnaG complex as containing homohexameric DnaB helicase. `PMID:14557266` Tougu and Marians 2003 stabilized the E. coli primase-helicase complex and measured DnaG primase occupancy on the DnaB hexamer.
DnaG primase	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	dnaG	3 primase copies per DnaB hexamer in the stabilized E. coli complex	UNKNOWN	Primase constituent that synthesizes RNA primer sequences while bound to DnaB helicase. `GO:1990156` GO:1990156 defines the DnaB-DnaG complex as containing DnaG primase. `PMID:14557266` Tougu and Marians 2003 reported three DnaG primase molecules per E. coli DnaB hexamer in their stabilized primase-helicase complex.

Taxonomic distribution

NCBITaxon:562 Escherichia coli — COMMON: Tougu and Marians 2003 stabilized the E. coli DnaB-DnaG primase-helicase complex. [PMID:14557266]

Canonical examples

NCBITaxon:562 Escherichia coli — Tougu and Marians 2003 used the E. coli DnaB-DnaG system to measure primase-helicase stoichiometry and primer synthesis on single-stranded DNA templates. [PMID:14557266]

Functions

DNA replication, synthesis of primer GO:0006269 — The DnaB-DnaG complex supports synthesis of RNA primers on single-stranded DNA templates during DNA replication.
- GO:1990156 GO:1990156 defines the DnaB-DnaG complex by DnaB-mediated unwinding and DnaG-mediated RNA primer synthesis.
- GO:0006269 GO:0006269 is the Gene Ontology biological process term for DNA replication primer synthesis.
- PMID:14557266 Tougu and Marians 2003 measured E. coli DnaB stimulation of DnaG-dependent primer synthesis on single-stranded templates.

Mechanism graphs

DnaB-DnaG supports primer synthesis (FUNCTION)

The DnaB helicase hexamer and DnaG primase form a complex that supports RNA primer synthesis on single-stranded DNA templates.

Subject	Predicate	Object	Evidence
DnaB helicase	contributes to	DnaB-DnaG complex	`GO:1990156` GO:1990156 defines the complex as containing homohexameric DnaB helicase.
DnaG primase	contributes to	DnaB-DnaG complex	`GO:1990156` GO:1990156 defines the complex as containing DnaG primase.
DnaB-DnaG complex	supports	DNA replication, synthesis of primer	`GO:1990156` GO:1990156 defines the complex by RNA primer synthesis during DNA replication and repair in Prokaryotes. `PMID:14557266` Tougu and Marians 2003 measured E. coli primer synthesis by DnaG in the presence of DnaB helicase.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral DnaB and DnaG family groundings for the DnaB-DnaG complex. GO:1990156 defines DnaB and DnaG as constituents of this primase-helicase complex. Exact source-neutral InterPro, Pfam, NCBIfam or UniProt family boundaries for these component classes need narrower curation before the labels can be grounded.
INTERPRETATION (RESOLVED): Model the GO:1990098 core primosome relationship as parthood rather than DnaB-DnaG complex is-a core primosome complex. OLS reports GO:0033202 as the direct GO:1990156 is-a parent and reports GO:1990098 as a separate hierarchical parent. GO:1990098 denotes a protein-DNA complex containing a helicase and primase, while GO:1990156 is a DnaB-DnaG protein complex.

Evidence

GO:1990156 Gene Ontology cellular-component term for the DnaB-DnaG complex and its related primosome-complex synonym.
GO:0033202 OLS reports GO:0033202 DNA helicase complex as the direct GO:1990156 is-a parent.
GO:1990098 OLS reports GO:1990098 core primosome complex as a direct hierarchical parent of GO:1990156.
GO:0006269 Gene Ontology biological-process term for DNA replication primer synthesis.
PMID:14557266 PubMed identifier for Tougu and Marians 2003, the Journal of Biological Chemistry paper cited by GO:1990156.
DOI:10.1074/jbc.M308956200 DOI for Tougu and Marians 2003, 'Mechanism and stoichiometry of interaction of DnaG primase with DnaB helicase of Escherichia coli in RNA primer synthesis', as reported by PubMed.

Curation history

2026-10-01T03:36:10Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-01T03:37:45Z codex · EXPANDED_RECORD — Added GO synonymy, DNA-helicase-complex parentage, core-primosome parthood, DnaB and DnaG reviewed-label-only components, E. coli scope, DNA-replication-primer-synthesis function evidence, GO/PubMed/DOI evidence, a nonmechanistic primer-synthesis graph, and grounding/parthood discussions.

Source: data/structures/other/dnab_dnag_complex.yaml