Structural Basis for Avoidance of Promutagenic DNA Repair by MutY Adenine DNA Glycosylase.
Publication Type:
Journal ArticleSource:
J Biol Chem, Volume 290, Issue 28, p.17096-105 (2015)Keywords:
Bacterial Proteins, Catalytic Domain, Crystallography, X-Ray, DNA Damage, DNA Glycosylases, DNA Repair, DNA, Bacterial, Geobacillus stearothermophilus, Guanine, Models, Molecular, Mutagenesis, Site-Directed, Mutation, Nucleic Acid Conformation, Protein Conformation, Recombinant Proteins, Substrate SpecificityAbstract:
<p>The highly mutagenic A:oxoG (8-oxoguanine) base pair in DNA most frequently arises by aberrant replication of the primary oxidative lesion C:oxoG. This lesion is particularly insidious because neither of its constituent nucleobases faithfully transmit genetic information from the original C:G base pair. Repair of A:oxoG is initiated by adenine DNA glycosylase, which catalyzes hydrolytic cleavage of the aberrant A nucleobase from the DNA backbone. These enzymes, MutY in bacteria and MUTYH in humans, scrupulously avoid processing of C:oxoG because cleavage of the C residue in C:oxoG would actually promote mutagenic conversion to A:oxoG. Here we analyze the structural basis for rejection of C:oxoG by MutY, using a synthetic crystallography approach to capture the enzyme in the process of inspecting the C:oxoG anti-substrate, with which it ordinarily binds only fleetingly. We find that MutY uses two distinct strategies to avoid presentation of C to the enzyme active site. Firstly, MutY possesses an exo-site that serves as a decoy for C, and secondly, repulsive forces with a key active site residue prevent stable insertion of C into the nucleobase recognition pocket within the enzyme active site.</p>