The C-terminal Lysine of Ogg2 DNA Glycosylases is a Major Molecular Determinant for Guanine/8-Oxoguanine Distinction

Abstract

7,8-dihydro-8-oxoguanine (8-oxoG) is a major oxidative lesion found in DNA. The 8-oxoguanine DNA glycosylases (Ogg) responsible for the removal of 8-oxoG are divided into three families: Ogg1, Ogg2 and AGOG. Since Ogg2 members are devoid of the recognition loop used by Ogg1 to discriminate between 8-oxoG and guanine it was unclear until recently how Ogg2 enzymes recognize the oxidized base. We present here the first crystallographic structure of an Ogg2 member, Methanocaldococcus janischii Ogg, in complex with a DNA duplex containing the 8-oxoG lesion. This structure highlights the critical role of the C-terminal lysine, strictly conserved in Ogg2, in the recognition of 8-oxoG. The structure also reveals that, similarly to Ogg1 glycosylases, Ogg2 undergoes a conformational change upon DNA binding. Furthermore, this work provides a structural rationale for the lack of opposite base specificity in this family of enzymes.

Recent advances in the structural mechanisms of DNA glycosylases

“…Despite very low sequence identity with hOGG1, structures of OGG2 from Methanocaldococcus janischii (MjOGG) and Sulfolobus solfataricus (SsOGG) confirmed that these enzymes adopt the HhH fold and contain the catalytic lysine and aspartate residues present in OGG1, but lack the N-terminal β-sheet domain [65] (Figure 4D). The structure of MjOGG in complex with 8oxoG-DNA illustrated that the OGG2 family of enzymes utilize a distinct mechanism for identification of 8oxoG in the active site, in which the C-terminal carboxylate group of Lys207, as opposed to the Gly42 backbone carbonyl interaction in hOGG1, interacts with the N7 of 8oxoG [84] (Figure 4E). Deletion of the three C-terminal residues abolished 8oxoG excision activity in MgOGG, but did not significantly affect enzyme integrity since the truncation only slightly diminished lyase activity [65].…”

Characterization of a Thermostable 8-Oxoguanine DNA Glycosylase Specific for GO/N Mismatches from the Thermoacidophilic ArchaeonThermoplasma volcanium

“…At Lys204, the ORF of TVG_RS00315 also possessed a C-terminal lysine (Lys207 in MjaOgg and Lys207 in SsoOgg) that discriminates between G and GO. In MjaOgg, Phe85 is wedged between the estranged cytosine and its 5′-neighbor, His133 and Trp198 sandwich the aberrant GO, and Arg84 interacts with the estranged cytosine [ 13 ]; all of these crucial residues were conserved in the putative TvoOgg, TVG_RS00315 ( Figure 1 ). These results strongly suggested that the ORF of TVG_RS00315, TvoOgg, is a homolog of Ogg2.…”

“…Ogg2 lacks amino acid residues Asn149, Arg154, and Tyr203 when compared to hOGG1, providing an explanation for Ogg2's reduced specificity, relative to Ogg1, for the base positioned opposite the lesion. The C-terminal lysine of Ogg2 may play a key role in discriminating between G and GO [ 13 ]. This prediction was confirmed by measuring the glycosylase/lyase activity of a deletion mutant of MjaOgg lacking the three amino acids at the C-terminal and subsequent cocrystallization of MjaOgg with DNA containing GO sequences [ 8 ].…”

Recognition of Damaged DNA: Structure and Dynamic Markers

“…The hOGG1 enzyme (a functional analog of Fpg/MutM in E. coli) preferentially recognizes 8-oxoG:C, while hOGG2 has similar functionality yet with less specificity for the opposite base. [84][85][86] The bacterial MutT enzyme (preserved in humans as the hMTH1 enzyme) recognizes 8-oxo-dGTP and produces monophosphates that cannot be incorporated during replication. 80 If 8-oxoG damage evades repair and is replicated with an A, MutY (human analog hMYH) can identify the 8-oxoG:A mispair and remove the A base.…”