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Nucleic Acids Res. 2016 Jan 29;44(2):801-10. doi: 10.1093/nar/gkv1469. Epub 2015 Dec 15.

Structure and stereochemistry of the base excision repair glycosylase MutY reveal a mechanism similar to retaining glycosidases.

Author information

1
Department of Chemistry, University of California, Davis, CA 95616, USA.
2
Department of Chemistry, University of California, Davis, CA 95616, USA Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA.
3
Department of Biology, University of Utah, Salt Lake City, UT 84112, USA martin.horvath@utah.edu.
4
Department of Chemistry, University of California, Davis, CA 95616, USA ssdavid@ucdavis.edu.

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.

PMID:
26673696
PMCID:
PMC4737165
DOI:
10.1093/nar/gkv1469
[Indexed for MEDLINE]
Free PMC Article

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