Structural and biochemical studies of a plant formamidopyrimidine-DNA glycosylase reveal why eukaryotic Fpg glycosylases do not excise 8-oxoguanine.
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 "αF-β9/10 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 "αF-β9/10 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.
Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, University of Vermont, Stafford Hall, Burlington, VT 05405-0068, USA. swallace@uvm.edu
Stéphanie
S
Duclos
Pierre
P
Aller
Pawel
P
Jaruga
Miral
M
Dizdaroglu
Susan S
SS
Wallace
Sylvie
S
Doublié
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D018736:DNA Adducts / Q000737:chemistry; D004260:DNA Repair; D043382:DNA-Formamidopyrimidine Glycosylase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005663:Furans / Q000737:chemistry; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D017354:Point Mutation; D017434:Protein Structure, Tertiary
D029681:Arabidopsis Proteins; D004247:DNA; D018736:DNA Adducts; D043382:DNA-Formamidopyrimidine Glycosylase; D005663:Furans; D006147:Guanine; C018674:tetrahydrofuran; C024829:8-hydroxyguanine; C468606:MMH-1 protein, Arabidopsis