Ferreira Henrique, Butler-Cole Ben, Burgin Alex, Baker Rachel, Sherratt David J, Arciszewska Lidia K
Division of Molecular Genetics, Biochemistry Department, University of Oxford, UK.
J Mol Biol. 2003 Jun 27;330(1):15-27. doi: 10.1016/s0022-2836(03)00558-8.
The tyrosine family site-specific recombinases XerC and XerD convert dimers of the Escherichia coli chromosome and many natural plasmids to monomers. The heterotetrameric recombination complex contains two molecules of XerC and two of XerD, with each recombinase mediating one pair of DNA strand exchanges. The two pairs of strand exchanges are separated in time and space. This demands that the catalytic activity of the four recombinase molecules be controlled so that only XerC or XerD is active at any given time, there being a switch in the recombinase activity state at the Holliday junction intermediate stage. Here, we analyse chimeras and deletion variants within the recombinase C-terminal domains in order to probe determinants that may be specific to either XerC or XerD, and to further understand how XerC-XerD interactions control catalysis in a recombining heterotetramer. The data confirm that the C-terminal "end" region of each recombinase plays an important role in coordinating catalysis within the XerCD heterotetramer and suggest that the interactions between the end regions of XerC and XerD and their cognate receptors within the partner recombinase are structurally and functionally different. The results support the hypothesis that the "normal" state in the heterotetrameric complex, in which XerC is catalytically active and XerD is inactive, depends on the interactions between the C-terminal end region of XerC and its receptor region within the C-terminal domain of XerD; interference with these interactions leads to a switch in the catalytic state, so that XerD is now preferentially active.
酪氨酸家族位点特异性重组酶XerC和XerD可将大肠杆菌染色体及许多天然质粒的二聚体转化为单体。异源四聚体重组复合物包含两个XerC分子和两个XerD分子，每个重组酶介导一对DNA链交换。这两对链交换在时间和空间上是分开的。这就要求控制四个重组酶分子的催化活性，以便在任何给定时间只有XerC或XerD具有活性，即在霍利迪连接中间体阶段重组酶活性状态会发生转换。在这里，我们分析了重组酶C末端结构域内的嵌合体和缺失变体，以探究可能对XerC或XerD具有特异性的决定因素，并进一步了解XerC - XerD相互作用如何在重组异源四聚体中控制催化作用。数据证实，每个重组酶的C末端“末端”区域在协调XerCD异源四聚体内的催化作用中发挥重要作用，并表明XerC和XerD的末端区域与其伙伴重组酶内的同源受体之间的相互作用在结构和功能上是不同的。结果支持这样的假设，即异源四聚体复合物中的“正常”状态，其中XerC具有催化活性而XerD无活性，取决于XerC的C末端区域与其在XerD的C末端结构域内的受体区域之间的相互作用；干扰这些相互作用会导致催化状态的转换，从而使XerD现在优先具有活性。
