5X3H : The Y81G mutant of the UNG crystal structure from Nitratifractor salsuginis
Experimental Technique/Method:X-RAY DIFFRACTION Resolution:2.5 Classification:DNA BINDING PROTEIN Release Date:2017-10-18 Deposition Date:2017-02-06 Revision Date:2017-12-13 Molecular Weight:60797.82 Macromolecule Type:Protein Residue Count:526 Atom Site Count:3837 DOI:10.2210/pdb5x3h/pdb Abstract: The uracil DNA glycosylase superfamily consists of at least six families with a diverse specificity toward DNA base damage. Family 1 uracil N-glycosylase (UNG) exhibits exclusive specificity on uracil-containing DNA. Here, we report a family 1 UNG homolog from Nitratifractor salsuginis with distinct biochemical features that differentiate it from conventional family 1 UNGs. Globally, the crystal structure of N. salsuginisUNG shows a few additional secondary structural elements. Biochemical and enzyme kinetic analysis, coupled with structural determination, molecular modeling, and molecular dynamics simulations, shows that N. salsuginisUNG contains a salt bridge network that plays an important role in DNA backbone interactions. Disruption of the amino acid residues involved in the salt bridges greatly impedes the enzymatic activity. A tyrosine residue in motif 1 (GQDPY) is one of the distinct sequence features setting family 1 UNG apart from other families. The crystal structure of Y81G mutant indicates that several subtle changes may account for its inactivity. Unlike the conventional family 1 UNG enzymes, N. salsuginisUNG is not inhibited by Ugi, a potent inhibitor specific for family 1 UNG. This study underscores the diversity of paths that a uracil DNA glycosylase may take to acquire its unique structural and biochemical properties during evolution.
Xie, Wei; Cao, Weiguo; Zhang, Zhemin; Chen, Ran (2017), "5X3H : The Y81G mutant of the UNG crystal structure from Nitratifractor salsuginis", RCSB-PDB, doi: 10.2210/pdb5x3h/pdb