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首页> 外文期刊>Journal of Molecular Biology >Cointegrase, a naturally occurring, truncated form of IS21 transposase, catalyzes replicon fusion rather than simple insertion of IS21
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Cointegrase, a naturally occurring, truncated form of IS21 transposase, catalyzes replicon fusion rather than simple insertion of IS21

机译：天然存在的IS21转座酶的截短形式的Cointegrase催化复制子融合，而不是IS21的简单插入。

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The bacterial insertion sequence IS21 contains two genes, istA and istB, which are organized as an operon. IS21 spontaneously forms tandem repeats designated (IS21),. Plasmids carrying (IS21), react efficiently with other replicons, producing cointegrates via a cut-and-paste mechanism. Here we show that transposition of a single IS21 element (simple insertion) and cointegrate formation involving (IS21), result from two distinct non-replicative pathways, which are essentially due to two differentiated IstA proteins, transposase and cointegrase. In Escherichia coli, transposase was characterized as the full-length, 46 kDa product of the istA gene, whereas the 45 kDa cointegrase was expressed, in-frame, from a natural internal translation start of istA. The istB gene, which could be experimentally disconnected from istA, provided a helper protein that strongly stimulated the transposase and cointegrase-driven reactions. Site-directed mutagenesis was used to express either cointegrase or transposase from the istA gene. Cointegrase promoted replicon fusion at high frequencies by acting on IS21 ends which were linked by 2, 3, or 4 bp junction sequences in (IS21),. By contrast, cointegrase poorly catalyzed simple insertion of IS21 elements. Transposase had intermediate, uniform activity in both pathways. The ability of transposase to synapse two widely spaced IS21 ends may reside in the eight N-terminal amino acid residues which are absent from cointegrase. Given the 2 or 3 bp spacing in naturally occurring IS21 tandems and the specialization of cointegrase, the fulminant spread of IS21 via cointegration can now be understood. (C) 1998 Academic Press. [References: 50]
机译：细菌插入序列IS21包含两个基因istA和istB，它们被组织为操纵子。 IS21自发形成称为（IS21）的串联重复序列。携带（IS21）的质粒与其他复制子有效反应，通过剪切和粘贴机制产生共整合体。在这里，我们显示单个IS21元素的转座（简单插入）和涉及（IS21）的共整合形成，是由两个不同的非复制途径引起的，这主要归因于两个分化的IstA蛋白，转座酶和共整合酶。在大肠杆菌中，转座酶的特征是istA基因的全长46 kDa产物，而45 kDa共整合酶则是从istA的自然内部翻译起始点按框表达的。 istB基因可以从istA上断开实验，它提供了一种辅助蛋白，可以强烈刺激转座酶和币整合酶驱动的反应。定点诱变用于表达istA基因的共整合酶或转座酶。共整合酶通过作用于IS21末端（在IS21中由2、3或4 bp的连接序列相连）而促进了复制子的融合。相比之下，协整酶不能很好地催化IS21元素的简单插入。转座酶在这两种途径中均具有中等活性。转座酶突触两个间隔较远的IS21末端的能力可能存在于共整合酶不存在的八个N末端氨基酸残基中。给定天然存在的IS21团簇中2或3 bp的间隔，以及cointegrase的特殊化，现在可以理解IS21通过协整的暴发性传播。 （C）1998年学术出版社。 [参考：50]

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