Searching for DNA Lesions: Structural Evidence for Lower- and Higher-Affinity DNA Binding Conformations of Human Alkyladenine DNA Glycosylase

• Main Authors: Setser, Jeremy W. (Author), Lingaraju, Gondichatnahalli M. (Author), Davis, C. Ainsley (Author), Samson, Leona D. (Author), Drennan, Catherine L (Author)
• Other Authors: Massachusetts Institute of Technology. Center for Environmental Health Sciences (Contributor), Massachusetts Institute of Technology. Department of Biological Engineering (Contributor), Massachusetts Institute of Technology. Department of Chemistry (Contributor), Koch Institute for Integrative Cancer Research at MIT (Contributor), Drennan, Catherine L. (Contributor)
• Format: Article
• Language: English
• Published: American Chemical Society, 2012-10-04T13:40:24Z.
• Subjects: Article
• Online Access: Get fulltext

 To efficiently repair DNA, human alkyladenine DNA glycosylase (AAG) must search the million-fold excess of unmodified DNA bases to find a handful of DNA lesions. Such a search can be facilitated by the ability of glycosylases, like AAG, to interact with DNA using two affinities: a lower-affinity interaction in a searching process and a higher-affinity interaction for catalytic repair. Here, we present crystal structures of AAG trapped in two DNA-bound states. The lower-affinity depiction allows us to investigate, for the first time, the conformation of this protein in the absence of a tightly bound DNA adduct. We find that active site residues of AAG involved in binding lesion bases are in a disordered state. Furthermore, two loops that contribute significantly to the positive electrostatic surface of AAG are disordered. Additionally, a higher-affinity state of AAG captured here provides a fortuitous snapshot of how this enzyme interacts with a DNA adduct that resembles a one-base loop.