4G4N

MutM containing M77A mutation bound to undamaged DNA

Summary for 4G4N

• Entry DOI: 10.2210/pdb4g4n/pdb
• Related: 4G4O 4G4Q 4G4R
• Descriptor: Formamidopyrimidine-DNA glycosylase, DNA (5'-D(P*AP*GP*GP*TP*AP*GP*AP*CP*TP*CP*GP*GP*AP*CP*GP*C)-3'), DNA (5'-D(*TP*GP*CP*GP*TP*CP*CP*GP*AP*GP*(TX2)P*CP*TP*AP*CP*C)-3'), ... (5 entities in total)
• Functional Keywords: dna glycosylase, dna repair, lesion recognition, base extrusion, disulfide crosslinking, hydrolase-dna complex, hydrolase/dna
• Biological source: Geobacillus stearothermophilus
• Total number of polymer chains: 3
• Total formula weight: 40446.11

Authors

Sung, R.J.,Zhang, M.,Qi, Y.,Verdine, G.L. (deposition date: 2012-07-16, release date: 2013-02-20, Last modification date: 2024-10-16)

Primary citation

Sung, R.J.,Zhang, M.,Qi, Y.,Verdine, G.L.
Structural and Biochemical Analysis of DNA Helix Invasion by the Bacterial 8-Oxoguanine DNA Glycosylase MutM.
J.Biol.Chem., 288:10012-10023, 2013

PubMed Abstract: MutM is a bacterial DNA glycosylase that serves as the first line of defense against the highly mutagenic 8-oxoguanine (oxoG) lesion, catalyzing glycosidic bond cleavage of oxoG to initiate base excision DNA repair. Previous work has shown that MutM actively interrogates DNA for the presence of an intrahelical oxoG lesion. This interrogation process involves significant buckling and bending of the DNA to promote extrusion of oxoG from the duplex. Structural snapshots have revealed several different highly conserved residues that are prominently inserted into the duplex in the vicinity of the target oxoG before and after base extrusion has occurred. However, the roles of these helix-invading residues during the lesion recognition and base extrusion process remain unclear. In this study, we set out to probe the function of residues Phe(114) and Met(77) in oxoG recognition and repair. Here we report a detailed biochemical and structural characterization of MutM variants containing either a F114A or M77A mutation, both of which showed significant decreases in the efficiency of oxoG repair. These data reveal that Met(77) plays an important role in stabilizing the lesion-extruded conformation of the DNA. Phe(114), on the other hand, appears to destabilize the intrahelical state of the oxoG lesion, primarily by buckling the target base pair. We report the observation of a completely unexpected interaction state, in which the target base pair is ruptured but remains fully intrahelical; this structure vividly illustrates the disruptive influence of MutM on the target base pair.

PubMed: 23404556
DOI: 10.1074/jbc.M112.415612

Experimental method

X-RAY DIFFRACTION (1.85 Å)