CONTACTS BETWEEN DNA GYRASE AND ITS BINDING-SITE ON DNA - FEATURES OF SYMMETRY AND ASYMMETRY REVEALED BY PROTECTION FROM NUCLEASES
CONTACTS BETWEEN DNA GYRASE AND ITS BINDING-SITE ON DNA - FEATURES OF SYMMETRY AND ASYMMETRY REVEALED BY PROTECTION FROM NUCLEASES
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DOI：
10.1073/pnas.78.3.1416
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发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
COZZARELLI, NR
中科院分区：
文献类型：
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作者：
MORRISON, A;COZZARELLI, NR
DNA螺旋酶[来自大肠杆菌]通过在特定的DNA位点上进行可逆的双链断裂，使一个DNA片段穿过另一个DNA片段，从而形成超级螺旋DNA。测定了2个高度优选的gyrase结合位点的核苷酸序列，并利用核酸酶保护分析了gyrase对DNA的吸附。gyrase的DNA断裂位点集中在大约50个碱基对（bp）的DNA中，这些DNA完全不受DNase I的影响，两侧的DNA区域平均间隔9.9个碱基对。拓扑异构酶II（一种与回转酶具有结构同源性的酶）对dna酶I具有相同的保护作用。DNA断裂的旋切酶位点在140 bp的DNA中偏离中心，免受外切酶III的酶切。ATP或gyrase抑制剂对DNase I保护的特异性作用不大。在加入ATP的不可水解类似物后，先前稳定的外切酶III屏障被侵入，新的屏障出现。本文还讨论了将这些结果与以往有关回转酶结构和机理的数据结合起来的详细模型。
DNA gyrase [from Escherichia coli] supercoils DNA by passing 1 DNA segment through another by means of a reversible double-strand break at specific DNA sites. The nucleotide sequence of 2 highly preferred gyrase binding sites was determined and the grip of gyrase on the DNA analyzed by using protection from nuclease attack. The DNA-breakage site of gyrase was centered in about 50 base pairs (bp) of DNA that was completely protected from DNase I and flanked by DNA regions cut at average intervals of 9.9 bases. The same pattern of protection from DNase I was observed with topoisomerase II'', an enzyme that shares structural homology with gyrase. The gyrase site of DNA breakage was off-center in the 140 bp of DNA protected from exonuclease III digestion. ATP or inhibitors of gyrase had little specific effect on DNase I protection. On addition of a nonhydrolyzable analog of ATP, previously stable barriers to exonuclease III were invaded and new barriers appeared. A detailed model uniting these results with previous data on gyrase structure and mechanism is discussed.