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Base-Independent DNA Base-Excision Repair of 8‑Oxoguanine
journal contribution
posted on 2018-03-26, 14:22 authored by Andrea Kreppel, Iris D. Blank, Christian OchsenfeldLiving organisms
protect their genome from gene mutation by excising
damaged DNA bases. Here, 8-oxoguanine (8OG) is one of the most abundant
DNA lesions. In bacteria the base excision is catalyzed by the enzyme
formamidopyrimidine-DNA- glycosylase (Fpg), for which two different
orientations of 8OG binding into the active site of Fpg have been
proposed: syn- and anti-conformation.
Here, we present a new ribose-protonated repair mechanism for 8OG
that is base-independent and can excise 8OG in both conformations.
Using high-level QM/MM calculations with up to 588/573 atoms in the
QM sphere, the activation barrier is computed in excellent agreement
with the experimentally measured value. Since the excised base itself
is not directly involved in the mechanism, this implies that lesion
discrimination does not occur within the active site of the enzyme.