DNA apurinic-apyrimidinic site binding and excision by endonuclease IV

Department of Molecular Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, MB4 La Jolla, California 92037, USA.
Nature Structural & Molecular Biology (Impact Factor: 11.63). 04/2008; 15(5):515-522. DOI: 10.1038/nsmb.1414

ABSTRACT Escherichia coli endonuclease IV is an archetype for an abasic or apurinic-apyrimidinic endonuclease superfamily crucial for DNA base excision repair. Here biochemical, mutational and crystallographic characterizations reveal a three–metal ion mechanism for damage binding and incision. The 1.10-Å resolution DNA-free and the 2.45-Å resolution DNA-substrate complex structures capture substrate stabilization by Arg37 and reveal a distorted Zn3-ligand arrangement that reverts, after catalysis, to an ideal geometry suitable to hold rather than release cleaved DNA product. The 1.45-Å resolution DNA-product complex structure shows how Tyr72 caps the active site, tunes its dielectric environment and promotes catalysis by Glu261-activated hydroxide, bound to two Zn2+ ions throughout catalysis. These structural, mutagenesis and biochemical results suggest general requirements for abasic site removal in contrast to features specific to the distinct endonuclease IV - triose phosphate isomerase (TIM) barrel and APE1 four-layer - folds of the apurinic-apyrimidinic endonuclease families.

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