School of Molecular Bioscience, The University of Sydney, New South Wales, Australia.
Microb Drug Resist. 2011 Sep;17(3):389-94. doi: 10.1089/mdr.2011.0037. Epub 2011 Jun 24.
The simplest form of transposon Tn5393 carries the strA and strB genes that confer resistance to streptomycin, in addition to its transposition determinants. Tn5393e, made up of Tn5393 and a second transposon, Tn6023, was found in an IncHI2 plasmid, pSRC125, recovered from a multiply antibiotic-resistant Salmonella enterica serovar Typhimurium isolate of bovine origin. Tn6023 is made up of the aphA1b gene flanked by two inversely oriented copies of insertion sequence (IS) IS26 and is flanked by an 8 bp duplication. It is related to several other transposons that carry aphA1b in fragments of differing length, also flanked by copies of IS26. Tn6023 is located in the tnpR gene of Tn5393, which lies upstream of the strA and strB genes, and the combined structure was designated Tn5393e. Although neither strA nor strB contain any mutations that would inactivate them, pSRC125 does not confer resistance to streptomycin, indicating that the strA and strB genes are not expressed. In Tn5393, strA and strB are transcribed from the tnpR promoter, and in Tn5393e neither this transcript nor the transcript from the aphA1b promoter in Tn6023 must reach strAB. Tn5393e was previously found in different locations in Corynebacteria, indicating that it can move and suggesting a wide distribution. The structures of several further variants of Tn5393 found in GenBank were analyzed and assigned variant designations Tn5393f-Tn5393i.
最简单的转座子 Tn5393 携带 strA 和 strB 基因，除了其转位决定子外，还赋予链霉素抗性。Tn5393e 由 Tn5393 和第二个转座子 Tn6023 组成，发现于来自牛源多重抗生素耐药鼠伤寒沙门氏菌分离株的 IncHI2 质粒 pSRC125 中。Tn6023 由 aphA1b 基因侧翼的两个反向取向的插入序列（IS）IS26 拷贝组成，两侧为 8bp 重复序列。它与其他几个携带 aphA1b 的转座子有关，这些转座子的 aphA1b 片段长度不同，也被 IS26 拷贝包围。Tn6023 位于 Tn5393 的 tnpR 基因内，位于 strA 和 strB 基因的上游，组合结构被命名为 Tn5393e。尽管 strA 和 strB 都没有任何使它们失活的突变，但 pSRC125 并不赋予链霉素抗性，表明 strA 和 strB 基因未表达。在 Tn5393 中，strA 和 strB 由 tnpR 启动子转录，而在 Tn5393e 中，这种转录本和 Tn6023 中 aphA1b 启动子的转录本都不能到达 strAB。Tn5393e 以前在棒状杆菌的不同位置发现，表明它可以移动，并暗示其广泛分布。在 GenBank 中分析了几种进一步的 Tn5393 变体的结构，并分配了变体指定 Tn5393f-Tn5393i。
