Residues of E. coli topoisomerase I conserved for interaction with a specific cytosine base to facilitate DNA cleavage.
Residues of E. coli topoisomerase I conserved for interaction with a specific cytosine base to facilitate DNA cleavage.
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DOI：
10.1093/nar/gks688
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发表时间：
2012-10
影响因子：
14.9
通讯作者：
Tse-Dinh YC
中科院分区：
文献类型：
--
作者：
Narula G;Tse-Dinh YC
细菌和古细菌拓扑异构酶I对DNA裂解位点上游4纳米的胞嘧啶碱基具有选择性。最近，对与单链寡核苷酸共价连接的大肠杆菌拓扑异构酶I的晶体结构的解析表明，R169和R173通过氢键与胞嘧啶碱基在−4位相互作用，而Y177的酚环在−4和−5位的碱基之间嵌入。将R169替换为丙氨酸改变了酶对- 4位碱基的选择性，从胞嘧啶变为腺嘌呤。R173A突变体表现出与野生型酶相似的序列选择性，但裂解和松弛活性较弱。Y177突变为丝氨酸或丙氨酸使酶失去活性。尽管这些残基中的每一个突变导致不同的结果，但R169、R173和Y177共同作用，与−4位置的胞嘧啶碱基相互作用，促进DNA切割。这些严格保守的残基可能在初始底物结合后作为分子调控因子形成蛋白质- DNA复合物，可剪切的磷酸盐位于活性位点，可被酪氨酸羟基亲核试剂切割DNA，从而促进反应途径中DNA的切割。
Bacterial and archaeal topoisomerase I display selectivity for a cytosine base 4 nt upstream from the DNA cleavage site. Recently, the solved crystal structure of Escherichia coli topoisomerase I covalently linked to a single-stranded oligonucleotide revealed that R169 and R173 interact with the cytosine base at the −4 position via hydrogen bonds while the phenol ring of Y177 wedges between the bases at the −4 and the −5 position. Substituting R169 to alanine changed the selectivity of the enzyme for the base at the −4 position from a cytosine to an adenine. The R173A mutant displayed similar sequence selectivity as the wild-type enzyme, but weaker cleavage and relaxation activity. Mutation of Y177 to serine or alanine rendered the enzyme inactive. Although mutation of each of these residues led to different outcomes, R169, R173 and Y177 work together to interact with a cytosine base at the −4 position to facilitate DNA cleavage. These strictly conserved residues might act after initial substrate binding as a Molecular Ruler to form a protein–DNA complex with the scissile phosphate positioned at the active site for optimal DNA cleavage by the tyrosine hydroxyl nucleophile to facilitate DNA cleavage in the reaction pathway.
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DOI：
10.1038/nrc2607
发表时间：
2009-05
期刊：
Nature reviews. Cancer
影响因子：
--
作者：
通讯作者：
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影响因子：
5
作者：
Collin, Frederic;Karkare, Shantanu;Maxwell, Anthony
通讯作者：
Maxwell, Anthony
DOI：
10.1073/pnas.0409851102
发表时间：
2005-03-01
影响因子：
11.1
作者：
Kim, JS;DeGiovanni, A;Kim, SH
通讯作者：
Kim, SH
影响因子：
--
作者：
Annamalai T;Dani N;Cheng B;Tse-Dinh YC
通讯作者：
Tse-Dinh YC
影响因子：
14.9
作者：
Tse-Dinh YC
通讯作者：
Tse-Dinh YC