Structural and biochemical studies of a plant formamidopyrimidine-DNA glycosylase reveal why eukaryotic Fpg glycosylases do not excise 8-oxoguanine
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- 作者：St¨¦phanie Duclos ; Pierre Aller ; Pawel Jaruga ; Miral Dizdaroglu ; Susan S. Wallace ; Sylvie Doubli¨¦
- 关键词：Base excision repair ; DNA glycosylase ; Abasic site ; 8-oxoguanine ; Fpg ; MutM
- 刊名：DNA Repair
- 出版年：2012
- 出版时间：1 September, 2012
- 年：2012
- 卷：11
- 期：9
- 页码：714-725
- 全文大小：1174 K
文摘
Formamidopyrimidine-DNA glycosylase (Fpg; MutM) is a DNA repair enzyme widely distributed in bacteria. Fpg recognizes and excises oxidatively modified purines, 4,6-diamino-5-formamidopyrimidine, 2,6-diamino-4-hydroxy-5-formamidopyrimidine and 8-oxoguanine (8-oxoG), with similar excision kinetics. It exhibits some lesser activity toward 8-oxoadenine. Fpg enzymes are also present in some plant and fungal species. The eukaryotic Fpg homologs exhibit little or no activity on DNA containing 8-oxoG, but they recognize and process its oxidation products, guanidinohydantoin (Gh) and spiroiminohydantoin (Sp). To date, several structures of bacterial Fpg enzymes unliganded or in complex with DNA containing a damaged base have been published but there is no structure of a eukaryotic Fpg. Here we describe the first crystal structure of a plant Fpg, Arabidopsis thaliana (AthFpg), unliganded and bound to DNA containing an abasic site analog, tetrahydrofuran (THF). Although AthFpg shares a common architecture with other Fpg glycosylases, it harbors a zincless finger, previously described in a subset of Nei enzymes, such as human NEIL1 and Mimivirus Nei1. Importantly the ¡°¦ÁF-¦Â9/10 loop¡± capping 8-oxoG in the active site of bacterial Fpg is very short in AthFpg. Deletion of a segment encompassing residues 213-229 in Escherichia coli Fpg (EcoFpg) and corresponding to the ¡°¦ÁF-¦Â9/10 loop¡± does not affect the recognition and removal of oxidatively damaged DNA base lesions, with the exception of 8-oxoG. Although the exact role of the loop remains to be further explored, it is now clear that this protein segment is specific to the processing of 8-oxoG.