Alteration of Escherichia coli topoisomerase IV conformation upon enzyme binding to positively supercoiled DNA
Alteration of Escherichia coli topoisomerase IV conformation upon enzyme binding to positively supercoiled DNA
复制标题
DOI：
10.1074/jbc.m603068200
复制
发表时间：
2006-07-14
影响因子：
4.8
通讯作者：
Cozzarelli, Nicholas R.
中科院分区：
文献类型：
--
作者：
Crisona, Nancy J.;Cozzarelli, Nicholas R.
大肠杆菌拓扑异构酶IV（topo IV）是一种必需的酶，在细胞分裂时解开子染色体以进行适当的分离。在体外，拓扑异构体IV容易区分两种可能的手性交叉段的DNA基板。这种酶松弛正超螺旋和左旋辫的速度是负超螺旋和右旋辫的20倍，并且具有更大的持续合成能力。在这里，我们使用拓扑异构酶IV的化学交联来证明与正超螺旋DNA结合的酶与与其他形式的DNA结合的酶处于不同的构象。使用三种不同的试剂，我们观察到新的拓扑异构酶IV的交联物种时，正超螺旋DNA在反应中。我们表明，帕雷亚基是在足够接近的交联时，酶被绑定到正超螺旋DNA。我们建议，改变的构象反映了有效的结合topo IV的两个DNA片段，参与链通道反应。
Escherichia coli topoisomerase IV (topo IV) is an essential enzyme that unlinks the daughter chromosomes for proper segregation at cell division. In vitro, topo IV readily distinguishes between the two possible chiralities of crossing segments in a DNA substrate. The enzyme relaxes positive supercoils and left-handed braids 20 times faster, and with greater processivity, than negative supercoils and right-handed braids. Here, we used chemical cross-linking of topo IV to demonstrate that enzyme bound to positively supercoiled DNA is in a different conformation from that bound to other forms of DNA. Using three different reagents, we observed novel cross-linked species of topo IV when positively supercoiled DNA was in the reaction. We show that the ParE subunits are in close enough proximity to be crosslinked only when the enzyme is bound to positively supercoiled DNA. We suggest that the altered conformation reflects efficient binding by topo IV of the two DNA segments that participate in the strand passage reaction.