1UT5 image
Entry Detail
PDB ID:
1UT5
Keywords:
Title:
Divalent metal ions (manganese) bound to T5 5'-exonuclease
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2003-12-04
Release Date:
2004-02-05
Method Details:
Experimental Method:
Resolution:
2.75 Å
R-Value Free:
0.33
R-Value Work:
0.25
Space Group:
P 43
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:EXODEOXYRIBONUCLEASE
Chain IDs:A, B
Chain Length:291
Number of Molecules:2
Biological Source:BACTERIOPHAGE T5
Ligand Molecules
Primary Citation
Roles of Divalent Metal Ions in Flap Endonuclease-Substrate Interactions
Nat.Struct.Mol.Biol. 11 450 ? (2004)
PMID: 15077103 DOI: 10.1038/NSMB754

Abstact

Flap endonucleases (FENs) have essential roles in DNA processing. They catalyze exonucleolytic and structure-specific endonucleolytic DNA cleavage reactions. Divalent metal ions are essential cofactors in both reactions. The crystal structure of FEN shows that the protein has two conserved metal-binding sites. Mutations in site I caused complete loss of catalytic activity. Mutation of crucial aspartates in site II abolished exonuclease action, but caused enzymes to retain structure-specific (flap endonuclease) activity. Isothermal titration calorimetry revealed that site I has a 30-fold higher affinity for cofactor than site II. Structure-specific endonuclease activity requires binding of a single metal ion in the high-affinity site, whereas exonuclease activity requires that both the high- and low-affinity sites be occupied by divalent cofactor. The data suggest that a novel two-metal mechanism operates in the FEN-catalyzed exonucleolytic reaction. These results raise the possibility that local concentrations of free cofactor could influence the endo- or exonucleolytic pathway in vivo.

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Primary Citation of related structures