Ross W, Landy A
Cell. 1983 May;33(1):261-72. doi: 10.1016/0092-8674(83)90355-0.
Int protein has two classes of binding sites within the phage att site: the arm-type recognition sequences are found in three specific sites that are distant from the region of strand exchange; the junction-type recognition sequences occur as inverted pairs around the crossover region in both attP and attB. During recombination between attP and attB each of the four DNA strands is cut at a homologous position within each of the junction-type Int binding sites. In all four junction-type sites Int protein interacts primarily with the same face of the DNA helix, as determined by those purine nitrogens that are protected against methylation by dimethylsulfate. Efficient secondary attachment sites for lambda contain sequences with partial homology to the junction-type binding sites. In addition, the sequence between, but not part of, the two junction-type sites (the overlap region) is strongly conserved in secondary att sites. Thus, in the vicinity of strand exchange, attP and a recombining partner, such as attB, are very similar; each comprises two junction-type Int recognition sites and an overlap (crossover) region.
整合蛋白（Int）在噬菌体附着位点（att位点）内有两类结合位点：臂型识别序列存在于三个特定位点，这些位点远离链交换区域；连接型识别序列以反向配对的形式出现在attP和attB的交叉区域周围。在attP和attB之间的重组过程中，四条DNA链中的每一条都在每个连接型Int结合位点内的同源位置被切断。在所有四个连接型位点中，Int蛋白主要与DNA螺旋的同一面相互作用，这是由那些能防止被硫酸二甲酯甲基化的嘌呤氮所决定的。λ噬菌体的有效二级附着位点包含与连接型结合位点具有部分同源性的序列。此外，两个连接型位点之间（但不属于连接型位点的部分）的序列（重叠区域）在二级附着位点中高度保守。因此，在链交换附近，attP和一个重组伙伴，如attB，非常相似；每个都包含两个连接型Int识别位点和一个重叠（交叉）区域。
