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Accueil du site > Animations Scientifiques > Séminaires 2007 > Structural insights into base damage recognition and removal by the Fpg DNA glycosylase
Structural insights into base damage recognition and removal by the Fpg DNA glycosylase
par Webmaster - 3 octobre 2007
Orateur :
Bertrand Castaing, Centre de Biophysique Moléculaire, CNRS, Orléans
Salle :
118
Sujet :
The Formamidopyrimidine-DNA glycosylase (Fpg) is a base excision DNA repair enzyme which removes from damaged DNA oxidized purines such as 7,8-dihydro-8-oxoguanine (8-oxoG) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG). These base lesions are pro-mutagenic (G:C to T:A transversions) and constitute replication blocks, respectively. Strategies to solve crystal structures of the Fpg protein from Lactococcus lactis (LlFpg) bound to the substrate analogue AP site- or FapydG-containing DNA will be described. The structures reveal that Fpg flips out the damaged nucleobase from the DNA double-helix and stabilizes it in an extra-helical conformation inside the enzyme substrate binding pocket. In such a flip out conformation, the base damage is exposed to Fpg catalysis residues for its excision from DNA. During this outstanding mechanism, Fpg specifies the nature of the damage recognizing all the hydrogen donors and acceptors of the oxidized purines and the nature of the orphan pyrimidine-containing the opposite DNA strand. Structures of Fpg bound to damage-containing DNA provide new insights into DNA glycosylase substrate specificity and catalysis.
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