Biological Assembly 1  

 3D View: Structure | Electron Density | Ligand Interaction

Global Symmetry: Cyclic - C6  (3D View)
Global Stoichiometry: Homo 6-mer - A6 

Biological assembly 1 assigned by authors.

Macromolecule Content

• Total Structure Weight: 85.13 kDa 
• Atom Count: 5868 
• Modelled Residue Count: 724 
• Deposited Residue Count: 736 
• Unique protein chains: 1

1N25

Crystal structure of the SV40 Large T antigen helicase domain

• DOI: 10.2210/pdb1N25/pdb

• Classification: VIRAL PROTEIN
• Organism(s): Macaca mulatta polyomavirus 1
• Expression System: Escherichia coli
• Mutation(s): No 


• Deposited: 2002-10-21 Released: 2003-06-03 
• Deposition Author(s): Li, D., Zhao, R., Lilyestrom, W., Gai, D., Zhang, R., DeCaprio, J.A., Fanning, E., Jochimiak, A., Szakonyi, G., Chen, X.S.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2.80 Å
• R-Value Free: 0.276 
• R-Value Work: 0.243 

Literature

Structure of the replicative helicase of the oncoprotein SV40 large tumour antigen

Li, D., Zhao, R., Lilyestrom, W., Gai, D., Zhang, R., DeCaprio, J.A., Fanning, E., Jochimiak, A., Szakonyi, G., Chen, X.S.

(2003) Nature 423: 512-518

• PubMed: 12774115 
• DOI: 10.1038/nature01691
• Primary Citation of Related Structures:  
  1N25


• PubMed Abstract: 
  

The oncoprotein large tumour antigen (LTag) is encoded by the DNA tumour virus simian virus 40. LTag transforms cells and induces tumours in animals by altering the functions of tumour suppressors (including pRB and p53) and other key cellular proteins. LTag is also a molecular machine that distorts/melts the replication origin of the viral genome and unwinds duplex DNA. LTag therefore seems to be a functional homologue of the eukaryotic minichromosome maintenance (MCM) complex. Here we present the X-ray structure of a hexameric LTag with DNA helicase activity. The structure identifies the p53-binding surface and reveals the structural basis of hexamerization. The hexamer contains a long, positively charged channel with an unusually large central chamber that binds both single-stranded and double-stranded DNA. The hexamer organizes into two tiers that can potentially rotate relative to each other through connecting alpha-helices to expand/constrict the channel, producing an 'iris' effect that could be used for distorting or melting the origin and unwinding DNA at the replication fork.

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Organizational Affiliation: 

Department of Biochemistry and Molecular Genetics, University of Colorado Health Science Center, School of Medicine, Denver, Colorado 80262, USA.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Large T Antigen	A, B	368	Macaca mulatta polyomavirus 1	Mutation(s): 0  EC: 3.6.4
Find proteins for P03070 (Simian virus 40) Explore P03070  Go to UniProtKB:  P03070

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
ZN	A, B	ZINC ION Zn PTFCDOFLOPIGGS-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.80 Å
• R-Value Free: 0.276 
• R-Value Work: 0.243 
• Space Group: P 3 2 1

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 120.321	α = 90
b = 120.321	β = 90
c = 132.202	γ = 120

Software Package:

Software Name	Purpose
HKL-2000	data collection
TRUNCATE	data reduction
SOLVE	phasing
CNS	refinement
HKL-2000	data reduction
CCP4	data scaling

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2002-10-21 
• Released Date: 2003-06-03 
Deposition Author(s): Li, D., Zhao, R., Lilyestrom, W., Gai, D., Zhang, R., DeCaprio, J.A., Fanning, E., Jochimiak, A., Szakonyi, G., Chen, X.S.

Revision History  

• Version 1.0: 2003-06-03
  Type: Initial release
  
• Version 1.1: 2008-04-28
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Version format compliance