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Crystal structure of a thwarted mismatch glycosylase DNA repair complex
Author(s) -
Barrett Tracey E.,
Schärer Orlando D.,
Savva Renos,
Brown Tom,
Jiricny Josef,
Verdine Gregory L.,
Pearl Laurence H.
Publication year - 1999
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/18.23.6599
Subject(s) - library science , biology , computer science
The bacterial mismatch‐specific uracil‐DNA glycosylase (MUG) and eukaryotic thymine‐DNA glycosylase (TDG) enzymes form a homologous family of DNA glycosylases that initiate base‐excision repair of G:U/T mismatches. Despite low sequence homology, the MUG/TDG enzymes are structurally related to the uracil‐DNA glycosylase enzymes, but have a very different mechanism for substrate recognition. We have now determined the crystal structure of the Escherichia coli MUG enzyme complexed with an oligonucleotide containing a non‐hydrolysable deoxyuridine analogue mismatched with guanine, providing the first structure of an intact substrate‐nucleotide productively bound to a hydrolytic DNA glycosylase. The structure of this complex explains the preference for G:U over G:T mispairs, and reveals an essentially non‐specific pyrimidine‐binding pocket that allows MUG/TDG enzymes to excise the alkylated base, 3, N 4 ‐ethenocytosine. Together with structures for the free enzyme and for an abasic‐DNA product complex, the MUG–substrate analogue complex reveals the conformational changes accompanying the catalytic cycle of substrate binding, base excision and product release.