NBU1 integrase: evidence for an altered recombination mechanism.
NBU1 integrase: evidence for an altered recombination mechanism.
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NBU1 整合酶：重组机制改变的证据。
DOI：
10.1111/j.1365-2958.2006.05073.x
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Gardner,JeffreyF
中科院分区：
文献类型：
--
作者：
Schmidt,JohnW;Rajeev,Lara;Salyers,AbigailA;Gardner,JeffreyF
NBU1 is a 10.3 kbpBacteroidesmobilizable transposon. A previous study had identified a 2.7 kbp segment of the excised circular intermediate that was sufficient to mediate integration of the element after transfer. This segment contained an integrase gene,intN1,and a region spanning the ends of the circular form within which integration occurred (attN1). The integrase protein, IntN1, appeared to be a member of the tyrosine recombinase family because it contains the canonical C‐terminal RKHRHY [RK(H/K)R(H/W)Y] motif that characterizes members of that family. In this study, we describe anEscherichia coli‐based integration assay system that has allowed us to characterizeattN1in detail. We first localizedattN1to a 250 bp region. We then used site‐directed mutations to identify directly repeated sequences withinattN1that were required for site‐specific integration. The locus of NBU1 site‐specific integration in theBacteroides thetaiotaomicronchromosome,attBT1‐1, contains a 14 bp sequence that is identical to a 14 bp sequence that spans the joined ends of the NBU1attN1site (common core sequences). The effects of mutations in the common core were different from the expected results if NBU1 integration was similar to λ integration. In particular single base changes near one end of the common core region, which introduced heterology, actually increased the frequency of integration. By contrast, compensating changes that restored homology in the common core region reduced the integration frequency. The recombination mechanism also differs from the one used by conjugative transposons that have coupling sequences between the sites of strand cleavage and exchange. These results indicate that although NBU1 integrase is considered to be a member of the tyrosine recombinase family, it catalyses an integrative recombination reaction that occurs by a different crossover mechanism.
