[Crystal structure and function of pyrimidine dimer specific excision repair enzyme: T4 endonuclease V]

Bacteriophage T4 endonuclease V is an enzyme which plays an important role in pyrimidine dimer specific excision repair of DNA. This enzyme possesses two distinct catalytic activities, pyrimidine dimer glycosylase and apyrimidinic endonuclease. The three dimensional structure (3D) of the wild type enzyme was determined at 1.45A resolution by X-ray crystallography. In combination with the results of site-directed mutagenesis, the refined structure revealed that Glu23 and the surrounding basic residues constitute the catalytic center of this enzyme. Furthermore, the 3D structure of active site mutants were determined and compared with that of the wild type. The results suggest that a precise configuration of Glu23 residue is required for glycosylation and that Arg3 plays an important role in the substrate binding.