title: Structure and stereochemistry of the base excision repair glycosylase MutY reveal a mechanism similar to retaining glycosidases.
abstract: MutY adenine glycosylases prevent DNA mutations by excising adenine from promutagenic 8-oxo-7,8-dihydroguanine (OG):A mismatches. Here, we describe structural features of the MutY active site bound to an azaribose transition state analog which indicate a catalytic role for Tyr126 and approach of the water nucleophile on the same side as the departing adenine base. The idea that Tyr126 participates in catalysis, recently predicted by modeling calculations, is strongly supported by mutagenesis and by seeing close contact between the hydroxyl group of this residue and the azaribose moiety of the transition state analog. NMR analysis of MutY methanolysis products corroborates a mechanism for adenine removal with retention of stereochemistry. Based on these results, we propose a revised mechanism for MutY that involves two nucleophilic displacement steps akin to the mechanisms accepted for 'retaining' O-glycosidases. This new-for-MutY yet familiar mechanism may also be operative in related base excision repair glycosylases and provides a critical framework for analysis of human MutY (MUTYH) variants associated with inherited colorectal cancer.
authors.affiliation: Department of Chemistry, University of California, Davis, CA 95616, USA.
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Woods
authors.affiliation: Department of Chemistry, University of California, Davis, CA 95616, USA Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Valerie L
authors.initials: VL
authors.lastname: O'Shea
authors.affiliation: Department of Chemistry, University of California, Davis, CA 95616, USA.
authors.forename: Aurea
authors.initials: A
authors.lastname: Chu
authors.affiliation: Department of Chemistry, University of California, Davis, CA 95616, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Cao
authors.affiliation: Department of Chemistry, University of California, Davis, CA 95616, USA.
authors.forename: Jody L
authors.initials: JL
authors.lastname: Richards
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, UT 84112, USA martin.horvath@utah.edu.
authors.forename: Martin P
authors.initials: MP
authors.lastname: Horvath
authors.affiliation: Department of Chemistry, University of California, Davis, CA 95616, USA ssdavid@ucdavis.edu.
authors.forename: Sheila S
authors.initials: SS
authors.lastname: David
mesh_terms: D000225:Adenine / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002384:Catalysis; D020134:Catalytic Domain; D045647:DNA Glycosylases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair; D001411:Geobacillus stearothermophilus / Q000737:chemistry; D006147:Guanine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D014443:Tyrosine; C024829:8-hydroxyguanine; D006147:Guanine; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase; D000225:Adenine