dnaB helicase

Replicative DNA helicase
Identifiers
Symbol	dnaB
Entrez	948555
UniProt	P0ACB0
Other data
EC number	3.6.1.-

DnaB-like helicase N terminal domain
nmr structure of the n-terminal domain of e. coli dnab helicase
Identifiers
Symbol	DnaB
Pfam	PF00772
InterPro	IPR007693
SCOP	1jwe
Available protein structures: Pfam structures PDB RCSB PDB; PDBe PDBsum structure summary

DnaB-like helicase C terminal domain
Identifiers
Symbol	DnaB_C
Pfam	PF03796
Pfam clan	CL0023
InterPro	IPR007694
Available protein structures: Pfam structures PDB RCSB PDB; PDBe PDBsum structure summary

dnaB helicase is an enzyme in bacteria which opens the replication fork during DNA replication. Although the mechanism by which DnaB both couples ATP hydrolysis to translocation along DNA and denatures the duplex is unknown, a change in the quaternary structure of the protein involving dimerisation of the N-terminal domain has been observed and may occur during the enzymatic cycle.^[1] Initially when DnaB binds to dnaA, it is associated with dnaC, a negative regulator. After DnaC dissociates, DnaB binds dnaG.

The N-terminal has a multi-helical structure that forms an orthogonal bundle.^[1] The C-terminal domain contains an ATP-binding site and is therefore probably the site of ATP hydrolysis.

In eukaryotes, helicase function is provided by the T antigen.

The DnaB helicase is the product of the dnaB gene. The helicase enzyme that is produced is a hexamer in E. coli, as well as in many other bacteria. The energy for DnaB activity is provided by NTP hydrolysis. Mechanical energy moves the DnaB into the replication fork, physically splitting it in half.

E. coli dnaB

In E. coli, dnaB is a hexameric protein of six 471 residue subunits, which form a ring-shaped structure with threefold symmetry. During DNA replication, the lagging strand of DNA binds in the central channel of dnaB, and the second DNA strand is excluded. The binding of dNTPs causes a conformational change which allows the dnaB to translocate along the DNA, thus mechanically forcing the separation of the DNA strands.

External links

• MeSH DnaB+Helicases

References

1. ^ ^{a b} Fass D, Bogden CE, Berger JM (June 1999). "Crystal structure of the N-terminal domain of the DnaB hexameric helicase". Structure 7 (6): 691–8. PMID 10404598. 

Replication

Prokaryotic (elongation)	DNA polymerase III holoenzyme (dnaC, dnaE, dnaH, dnaN, dnaQ, dnaT, dnaX) · Replisome · DNA ligase · DNA clamp · Topoisomerase (DNA gyrase) Prokaryotic DNA polymerase: DNA polymerase I (Klenow fragment)
Eukaryotic (synthesis in S phase)	Replication factor C (RFC1) · Flap endonuclease (FEN1) · Topoisomerase · Replication protein A (RPA1) Eukaryotic DNA polymerase: delta (POLD1, POLD2, POLD3, POLD4) DNA clamp (PCNA)
Both	Movement: Processivity · DNA ligase

Termination

Telomere: Telomerase (TERT, TERC, DKC1)

see also DNA replication and repair-deficiency disorder
B bsyn: dna (repl, cycl, reco, repr) · tscr (fact, tcrg, nucl, rnat, rept, ptts) · tltn (risu, pttl, nexn) · dnab, rnab/runp · stru (domn, 1°, 2°, 3°, 4°)

This article includes text from the public domain Pfam and InterPro IPR007693

This article includes text from the public domain Pfam and InterPro IPR007694