BACTERIAL-DNA TOPOISOMERASE-I CAN RELAX POSITIVELY SUPERCOILED DNA CONTAINING A SINGLE-STRANDED LOOP
BACTERIAL-DNA TOPOISOMERASE-I CAN RELAX POSITIVELY SUPERCOILED DNA CONTAINING A SINGLE-STRANDED LOOP
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DOI：
10.1016/0022-2836(85)90075-0
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发表时间：
1985-01-01
影响因子：
5.6
通讯作者：
WANG, JC
中科院分区：
文献类型：
--
作者：
KIRKEGAARD, K;WANG, JC
使用异源双链分子形成的一对质粒，其中之一包含一个小的缺失相对于其他的，它表明，细菌拓扑异构酶I可以放松一个积极的超螺旋DNA，如果一个短的单链环被放置在DNA。这一结果支持了以下假设，即细菌DNA拓扑异构酶I在其松弛反应中对负超螺旋DNA的特异性来自于活性酶-底物复合物中短单链DNA片段的要求。对细菌DNA拓扑异构酶I和含有长度范围为13至27个核苷酸的单链环的异源双链DNA分子之间的复合物进行的核溶解和化学探测表明，该酶特异性结合含有单链环的区域;拓扑异构酶切割DNA的位点似乎位于单链环内，酶与切割点两侧的核苷酸相互作用。
Using heteroduplex molecules formed from a pair of plasmids, one of which contains a small deletion relative to the other, it is shown that bacterial topoisomerase I can relax a positively supercoiled DNA if a short single-stranded loop is placed in the DNA. This result supports the postulate that the specificity of bacterial DNA topoisomerase I for negatively supercoiled DNA in its relaxation reaction derives from the requirement of a short single-stranded DNA segment in the active enzyme-substrate complex. Nucleolytic and chemical probing of complexes between bacterial DNA topoisomerase I and heteroduplex DNA molecules containing single-stranded loops ranging from 13 to 27 nucleotides in length suggests that the enzyme binds specifically to the region containing a single-stranded loop; the site of DNA cleavage by the topoisomerase appears to lie within the single-stranded loop, with the enzyme interacting with nucleotides on both sides of the point of cleavage.