Crystal structure of a thwarted mismatch glycosylase DNA repair complex
Crystal structure of a thwarted mismatch glycosylase DNA repair complex
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DOI：
10.1093/emboj/18.23.6599
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发表时间：
1999-12-01
期刊：
影响因子：
11.4
通讯作者：
Pearl, LH
中科院分区：
文献类型：
--
作者：
Barrett, TE;Schärer, OD;Pearl, LH
细菌错配特异性尿嘧啶-DNA糖基酶（MUG）和真核胸腺嘧啶-DNA糖基酶（TDG）酶形成同源DNA糖基酶家族，启动碱基切除修复G:U/T错配。尽管序列同源性较低，但MUG/TDG酶在结构上与尿嘧啶- dna糖基酶相关，但对底物的识别机制却截然不同。我们现在已经确定了大肠杆菌R-IUG酶与含有与鸟嘌呤不匹配的不可水解脱氧尿苷类似物的寡核苷酸络合的晶体结构，提供了完整底物的第一个结构-核苷酸有效地结合水解DNA糖基酶。该配合物的结构解释了G:U对G:T错对的偏好，并揭示了一个本质上非特异性的嘧啶结合袋，允许MUG/TDG酶去除烷基化碱基3，n -4-乙基胞嘧啶。与游离酶和碱基- dna产物复合物的结构一起，MUG-底物模拟复合物揭示了伴随底物结合、碱基去除和产物释放的催化循环的构象变化。
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 R-IUG 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.