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Mutat Res. 2000 Aug 30;460(3-4):201-10.

Structural studies of human alkyladenine glycosylase and E. coli 3-methyladenine glycosylase.

Author information

1
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.

Abstract

Human alkyladenine glycosylase (AAG) and Escherichia coli 3-methyladenine glycosylase (AlkA) are base excision repair glycosylases that recognize and excise a variety of alkylated bases from DNA. The crystal structures of these enzymes have provided insight into their substrate specificity and mechanisms of catalysis. Both enzymes utilize DNA bending and base-flipping mechanisms to expose and bind substrate bases. Crystal structures of AAG complexed to DNA suggest that the enzyme selects substrate bases through a combination of hydrogen bonding and the steric constraints of the active site, and that the enzyme activates a water molecule for an in-line backside attack of the N-glycosylic bond. In contrast to AAG, the structure of the AlkA-DNA complex suggests that AlkA substrate recognition and catalytic specificity are intimately integrated in a S(N)1 type mechanism in which the catalytic Asp238 directly promotes the release of modified bases.

PMID:
10946229
DOI:
10.1016/s0921-8777(00)00027-6
[Indexed for MEDLINE]

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