Rojo F, Alonso J C
Centro Nacional de Biotecnología, CSIC, Campus de la Universidad Autónoma de Madrid, Cantoblanco, Spain.
Nucleic Acids Res. 1995 Aug 25;23(16):3181-8. doi: 10.1093/nar/23.16.3181.
The beta recombinase from plasmid pSM19035 catalyzes intramolecular site-specific recombination between two directly or inversely oriented six sites in the presence of a chromatin-associated protein (Hbsu, HU or HMG-1). The six site is a DNA segment containing two binding sites (I and II) for beta protein dimers. We show that beta recombinase binds sequentially to both sites, having a different affinity for each one. Hydroxyl radical footprints show a different protection pattern at each site. Positions critical for beta protein binding have been identified by methylation interference and missing nucleoside assays. The results indicate that the protein recognizes each site in a different way. Comparison of the beta protein recombination site with that of DNA resolvases and DNA invertases of the Tn3 family, to which it belongs, shows that these sequences can be divided into two regions. One corresponds to the crossover point and is similar for all recombinases of the family. The other region differs in the different subfamilies and seems to have an architectural role in aligning the crossover sites at the synaptic complex. The different ways to assemble this complex could explain why each system leads to a particular recombination event: DNA resolution (resolvases), inversion (invertases) or both (beta recombinase).
来自质粒pSM19035的β重组酶在一种与染色质相关的蛋白质（Hbsu、HU或HMG-1）存在的情况下，催化两个同向或反向排列的六个位点之间的分子内位点特异性重组。六个位点是一个包含β蛋白二聚体的两个结合位点（I和II）的DNA片段。我们发现β重组酶依次与两个位点结合，对每个位点的亲和力不同。羟基自由基足迹显示每个位点有不同的保护模式。通过甲基化干扰和缺失核苷分析确定了对β蛋白结合至关重要的位置。结果表明该蛋白质以不同方式识别每个位点。将β蛋白重组位点与其所属的Tn3家族的DNA解离酶和DNA倒位酶的重组位点进行比较，发现这些序列可分为两个区域。一个区域对应于交叉点，该家族的所有重组酶都相似。另一个区域在不同亚家族中有所不同，似乎在突触复合物中使交叉位点对齐方面具有结构作用。组装该复合物的不同方式可以解释为什么每个系统会导致特定的重组事件：DNA解离（解离酶）、倒位（倒位酶）或两者皆有（β重组酶）。
