Department of Microbiology and College of Medicine, University of Illinois, Urbana, IL 61801, USA.
Nucleic Acids Res. 2010 Jan;38(3):958-69. doi: 10.1093/nar/gkp927. Epub 2009 Dec 1.
The Bacteroides conjugative transposon CTnDOT encodes an integrase, IntDOT, which is a member of the tyrosine recombinase family. Other members of this group share a strict requirement for sequence identity within the region of strand exchange, called the overlap region. Tyrosine recombinases catalyze recombination by making an initial cleavage, strand exchange and ligation, followed by strand swapping isomerization requiring sequence identity in the overlap region, followed by the second cleavage, strand exchange and ligation. IntDOT is of particular interest because it has been shown to utilize a three-step mechanism: a sequence identity-dependent initial strand exchange that requires two base pairs of complementary DNA at the site of cleavage; a sequence identity-independent strand swapping isomerization, followed by a sequence identity-independent cleavage, strand exchange and ligation. In addition to the sequence identity requirement in the overlap region, Lambda Int interactions with arm-type sites dictate the order of strand exchange regardless of the orientation of the overlap region. Although IntDOT has an arm-binding domain, we show here that the location of sequence identity within the overlap region dictates where the initial cleavage takes place and that IntDOT can recombine substrates containing mismatches in the overlap region so long as a single base of sequence identity exists at the site of initial cleavage.
拟杆菌属细菌接合转座子 CTnDOT 编码一种整合酶 IntDOT，它属于酪氨酸重组酶家族成员。该组的其他成员在称为重叠区域的链交换区域内具有严格的序列同一性要求。酪氨酸重组酶通过初始切割、链交换和连接、随后需要重叠区域中的序列同一性的链交换异构化、随后是第二次切割、链交换和连接来催化重组。IntDOT 特别有趣，因为它已被证明采用三步机制：依赖序列同一性的初始链交换，需要在切割位点处具有两个碱基对的互补 DNA；序列同一性非依赖性链交换异构化，随后是序列同一性非依赖性切割、链交换和连接。除了重叠区域中的序列同一性要求外，Lambda Int 与臂型位点的相互作用决定了链交换的顺序，而不管重叠区域的方向如何。尽管 IntDOT 具有臂结合结构域，但我们在这里表明，重叠区域内序列同一性的位置决定了初始切割发生的位置，并且 IntDOT 可以重组含有重叠区域中错配的底物，只要在初始切割位点存在单个碱基的序列同一性即可。
