Tsuda M, Genka H
Department of Environmental Life Science, Graduate School of Life Sciences, Tohoku University, Katahira 2-1-1, Sendai 980-8577, Japan.
J Bacteriol. 2001 Nov;183(21):6215-24. doi: 10.1128/JB.183.21.6215-6224.2001.
It has been reported that the toluene-degrading (xyl) genes from Pseudomonas putida plasmid pWW53 are able to translocate to broad-host-range drug resistance plasmid RP4, and pWW53-4 is one of the smallest RP4 derivatives (H. Keil, S. Keil, R. W. Pickup, and P. A. Williams, J. Bacteriol. 164:887-895, 1985). Our investigation of pWW53-4 in this study demonstrated that such a translocated region that is 39 kb long is a transposon. This mobile element, Tn4656, was classified as a class II transposon since its transposition occurred by a two-step process: transposase (TnpA)-mediated formation of the cointegrate and resolvase (TnpR)-mediated site-specific resolution of the cointegrate at the two copies of the res site. The Tn4656 TnpA and TnpR functions encoded in the rightmost 4-kb region were found to be exchangeable with those specified by other Tn1721-related class II transposons, including another toluene transposon, Tn4653. Sequence analysis of the transposition-related genes and sites of Tn4656 also supported the hypothesis that this transposon is closely related to the Tn1721-related transposons. The lower transposition frequency of Tn4656 has been suggested to be due to the unique nucleotide sequence of one of the terminal 39-bp inverted repeats.
据报道,恶臭假单胞菌质粒pWW53上的甲苯降解(xyl)基因能够转移至广宿主范围的耐药性质粒RP4,而pWW53 - 4是最小的RP4衍生物之一(H. 凯尔、S. 凯尔、R. W. 皮卡普和P. A. 威廉姆斯,《细菌学杂志》164:887 - 895,1985年)。我们在本研究中对pWW53 - 4的研究表明,这样一个长度为39 kb的转移区域是一个转座子。这个移动元件Tn4656被归类为II类转座子,因为它的转座通过两步过程发生:转座酶(TnpA)介导共合体的形成以及解离酶(TnpR)介导在res位点的两个拷贝处共合体的位点特异性解离。发现在最右侧4 kb区域编码的Tn4656 TnpA和TnpR功能可与其他Tn1721相关的II类转座子(包括另一个甲苯转座子Tn4653)所指定的功能互换。对Tn4656转座相关基因和位点的序列分析也支持了这一转座子与Tn1721相关转座子密切相关的假说。有人提出Tn4656较低转座频率是由于末端39 bp反向重复序列之一的独特核苷酸序列所致。