Genomic and functional analysis of the IncP-9 naphthalene-catabolic plasmid NAH7 and its transposon Tn4655 suggests catabolic gene spread by a tyrosine recombinase
Genomic and functional analysis of the IncP-9 naphthalene-catabolic plasmid NAH7 and its transposon Tn4655 suggests catabolic gene spread by a tyrosine recombinase
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DOI：
10.1128/jb.00185-06
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发表时间：
2006-06-01
影响因子：
3.2
通讯作者：
Tsuda, M
中科院分区：
文献类型：
--
作者：
Sota, M;Yano, H;Tsuda, M
来自恶臭假单胞菌G7的不相容群P - 9（IncP - 9）可自我传递的质粒NAH7上的萘降解（nah）基因是细菌好氧降解芳香烃的一些被广泛研究的遗传决定因素。与对其降解级联和酶功能的详细研究相比，质粒NAH7的生物学特性仍不清楚。我们在本研究中的序列测定以及先前提交的序列揭示了NAH7的整个结构（82232bp）。将NAH7与另外两个已完全测序的IncP - 9降解质粒pDTG1和pWW0进行比较，发现这三个质粒在编码基本质粒功能（IncP - 9骨架）的39kb区域具有非常高的核苷酸相似性。从系统发育角度来看，NAH7的骨架与pDTG1的骨架比与pWW0的更相关。这三个质粒在IncP - 9骨架上的不同位置携带它们的降解基因簇。所有由NAH7指定的nah基因都位于一个11类转座子Tn4655上。我们对Tn4655编码的位点特异性重组系统的分析表明：（i）一种新型酪氨酸重组酶TnpI催化两个attI位点拷贝之间的分子内和分子间重组；（ii）功能性attI位点位于一个119bp的片段内；（iii）位点特异性链交换发生在41bp的CORE位点内的一个30bp片段中。我们的结果以及其他萘降解质粒pDTG1和pND6 - 1的序列数据表明，TnpI - attI重组系统在这些降解质粒的建立中具有潜在作用。
The naphthalene-catabolic (nah) genes on the incompatibility group P-9 (IncP-9) self-transmissible plasmid NAH7 from Pseudomonas putida G7 are some of the most extensively characterized genetic determinants for bacterial aerobic catabolism of aromatic hydrocarbons. In contrast to the detailed studies of its catabolic cascade and enzymatic functions, the biological characteristics of plasmid NAH7 have remained unclear. Our sequence determination in this study together with the previously deposited sequences revealed the entire structure of NAH7 (82,232 bp). Comparison of NAH7 with two other completely sequenced IncP-9 catabolic plasmids, pDTG1 and pWW0, revealed that the three plasmids share very high nucleotide similarities in a 39-kb region encoding the basic plasmid functions (the IncP-9 backbone). The backbone of NAH7 is phylogenetically more related to that of pDTG1 than that of pWW0. These three plasmids carry their catabolic gene clusters at different positions on the IncP-9 backbone. All of the NAH7-specified nah genes are located on a class 11 transposon, Tn4655. Our analysis of the Tn4655-encoded site-specific recombination system revealed that (i) a novel tyrosine recombinase, TnpI, catalyzed both the intra- and intermolecular recombination between two copies of the attI site, (ii) the functional attI site was located within a 119-bp segment, and (iii) the site-specific strand exchange occurred within a 30-bp segment in the 41-bp CORE site. Our results and the sequence data of other naphthalene-catabolic plasmids, pDTG1 and pND6-1, suggest a potential role of the TnpI-attI recombination system in the establishment of these catabolic plasmids.