Biological Assembly 1  

 3D View: Structure | Electron Density

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Homo 7-mer - A7 

Biological assembly 1 assigned by authors and generated by PISA (software)

Macromolecule Content

• Total Structure Weight: 391.00 kDa 
• Atom Count: 26208 
• Modelled Residue Count: 3381 
• Deposited Residue Count: 3521 
• Unique protein chains: 1

1Q57

The Crystal Structure of the Bifunctional Primase-Helicase of Bacteriophage T7

• DOI: 10.2210/pdb1Q57/pdb

• Classification: TRANSFERASE
• Organism(s): Escherichia phage T7
• Expression System: Escherichia coli
• Mutation(s): Yes 


• Deposited: 2003-08-06 Released: 2003-11-25 
• Deposition Author(s): Toth, E.A., Li, Y., Sawaya, M.R., Cheng, Y., Ellenberger, T.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 3.45 Å
• R-Value Free: 0.326 
• R-Value Work: 0.299 
• R-Value Observed: 0.301 

Literature

The Crystal Structure of the Bifunctional Primase-Helicase of Bacteriophage T7

Toth, E.A., Li, Y., Sawaya, M.R., Cheng, Y., Ellenberger, T.

(2003) Mol Cell 12: 1113-1123

• PubMed: 14636571 
• DOI: 10.1016/s1097-2765(03)00442-8
• Primary Citation of Related Structures:  
  1Q57


• PubMed Abstract: 
  

Within minutes after infecting Escherichia coli, bacteriophage T7 synthesizes many copies of its genomic DNA. The lynchpin of the T7 replication system is a bifunctional primase-helicase that unwinds duplex DNA at the replication fork while initiating the synthesis of Okazaki fragments on the lagging strand. We have determined a 3.45 A crystal structure of the T7 primase-helicase that shows an articulated arrangement of the primase and helicase sites. The crystallized primase-helicase is a heptamer with a crown-like shape, reflecting an intimate packing of helicase domains into a ring that is topped with loosely arrayed primase domains. This heptameric isoform can accommodate double-stranded DNA in its central channel, which nicely explains its recently described DNA remodeling activity. The double-jointed structure of the primase-helicase permits a free range of motion for the primase and helicase domains that suggests how the continuous unwinding of DNA at the replication fork can be periodically coupled to Okazaki fragment synthesis.

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Organizational Affiliation: 

Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
DNA primase/helicase	A, B, C, D, E, F, G	503	Escherichia phage T7	Mutation(s): 2  Gene Names: 4 EC: 2.7.7 (PDB Primary Data), 3.6.4.12 (UniProt)
Find proteins for P03692 (Escherichia phage T7) Explore P03692  Go to UniProtKB:  P03692

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 3.45 Å
• R-Value Free: 0.326 
• R-Value Work: 0.299 
• R-Value Observed: 0.301 
• Space Group: P 1 2₁ 1

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 117.179	α = 90
b = 171.567	β = 99.86
c = 118.581	γ = 90

Software Package:

Software Name	Purpose
REFMAC	refinement
HKL-2000	data reduction
SCALEPACK	data scaling
SHARP	phasing

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2003-08-06 
• Released Date: 2003-11-25 
Deposition Author(s): Toth, E.A., Li, Y., Sawaya, M.R., Cheng, Y., Ellenberger, T.

Revision History  

• Version 1.0: 2003-11-25
  Type: Initial release
  
• Version 1.1: 2008-04-29
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Advisory, Version format compliance