Duplex DNA knots produced by Escherichia coli topoisomerase I. Structure and requirements for formation.
Duplex DNA knots produced by Escherichia coli topoisomerase I. Structure and requirements for formation.
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DOI：
10.1016/s0021-9258(18)89168-2
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发表时间：
1985-04
期刊：
影响因子：
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通讯作者：
F. Dean;A. Stasiak;T. Koller;N. Cozzarelli
中科院分区：
文献类型：
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作者：
F. Dean;A. Stasiak;T. Koller;N. Cozzarelli
我们系统地研究了大肠杆菌拓扑异构酶 I 对带切口的环状双链 DNA 的打结。结的琼脂糖凝胶电泳形成了 DNA 带的阶梯。每个梯级由具有相同数量节点或段交叉点的各种结组成；相邻横档中的结相差一个节点。我们将recA蛋白包被的DNA的电子显微镜技术扩展到拓扑异构酶I所打结的复杂结的可视化。令人惊讶的结果是，该酶产生了理论上可能的每个结。形成复杂结需要过量的酶，这表明拓扑异构酶 I 除了促进链通过之外，还具有扭曲 DNA 的作用。我们得出的结论是，形成的节点同样可能是阳性或阴性，并且拓扑异构酶 I 可以使 DNA 链通过瞬时酶产生的断裂，而不考虑通过链的方向。结果根据打结拓扑要求的公式进行解释。
We investigated systematically the knotting of nicked circular duplex DNA by Escherichia coli topoisomerase I. Agarose gel electrophoresis of knots forms a ladder of DNA bands. Each rung is made up of a variety of knots with the same number of nodes, or segment crossings; knots in adjacent rungs differ by one node. We extended the technique of electron microscopy of recA protein-coated DNA to the visualization of the complex knots tied by topoisomerase I. The striking result is that the enzyme produces every knot theoretically possible. The requirement for excess enzyme to form complex knots suggests a role for topoisomerase I in contorting the DNA in addition to promoting strand passage. We conclude that nodes formed are equally likely to be positive or negative and that topoisomerase I can pass DNA strands through a transient enzyme-generated break without regard to orientation of the passing strand. The results are interpreted in terms of a formulation for the topological requirements for knotting.