SITE-SPECIFIC RELAXATION AND RECOMBINATION BY THE TN3 RESOLVASE - RECOGNITION OF THE DNA PATH BETWEEN ORIENTED RES SITES
SITE-SPECIFIC RELAXATION AND RECOMBINATION BY THE TN3 RESOLVASE - RECOGNITION OF THE DNA PATH BETWEEN ORIENTED RES SITES
复制标题
DOI：
10.1016/0092-8674(83)90312-4
复制
发表时间：
1983-01-01
期刊：
影响因子：
64.5
通讯作者：
COZZARELLI, NR
中科院分区：
文献类型：
--
作者：
KRASNOW, MA;COZZARELLI, NR
研究了大肠杆菌转座子Tn3编码的解旋酶进行定点重组的动力学。纯酶重组的超螺旋载体含有2个直接重复的重组位点，称为RES位点。Resolvase是一种严格定位的拓扑异构酶。它只松弛含有直接重复的RES位点的质粒；含有0、1或2个倒置位点的底物是惰性的。即使当通过将质粒与单个位点连接来确保RES位点的接近时，也不会发生松弛或重组。重组的两个环状产物只有一次是环状链环。分解酶的这些性质要求DNA在RES位点之间的路径被清楚地定义，并且链交换以独特的几何形式发生。二聚体分解酶的1个亚基结合在1个Res位点，而其他亚基沿着相邻的DNA搜索直到与第二个位点相遇，这一模型解释了分解酶区分分子内和分子间位点、感知位点的相对方向和产生单一相互连接的链烷的能力。因为解旋酶是一种1型拓扑异构酶，它可能一次造成重组所需的双链DNA断裂。
The dynamics of site-specific recombination by the resolvase encoded by the Escherichia coli transposon Tn3 were studied. The pure enzyme recombined supercoiled plasmids containing 2 directly repeated recombination sites, called res sites. Resolvase is a strictly site-specific topoisomerase. It relaxed only plasmids containing directly repeated res sites; substrates with 0, 1 or 2 inverted sites were inert. Even when the proximity of res sites was ensured by catenation of plasmids with a single site, neither relaxation nor recombination occurred. The 2 circular products of recombination were catenanes interlinked only once. These properties of resolvase require that the path of the DNA between res sites be clearly defined and that strand exchange occur with a unique geometry. A model in which 1 subunit of a dimeric resolvase is bound at 1 res site, while the other searches along adjacent DNA until it encounters the 2nd site, would account for the ability of resolvase to distinguish intramolecular from intermolecular sites, to sense the relative orientation of sites and to produce singly interlinked catenanes. Because resolvase is a type 1 topoisomerase, it probably makes the required duplex DNA breaks of recombination 1 strand at a time.