Kahn K, Schaefer M R
Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City 64110, USA.
J Bacteriol. 1995 Dec;177(24):7026-32. doi: 10.1128/jb.177.24.7026-7032.1995.
A transposon, designated Tn5469, was isolated from mutant strain FdR1 of the filamentous cyanobacterium Fremyella diplosiphon following its insertion into the rcaC gene. Tn5469 is a 4,904-bp noncomposite transposon with 25-bp near-perfect terminal inverted repeats and has three tandemly arranged, slightly overlapping potential open reading frames (ORFs) encoding proteins of 104.6 kDa (909 residues), 42.5 kDa (375 residues), and 31.9 kDa (272 residues). Insertion of Tn5469 into the rcaC gene in strain FdR1 generated a duplicate 5-bp target sequence. On the basis of amino acid sequence identifies, the largest ORF, designated tnpA, is predicted to encode a composite transposase protein. A 230-residue domain near the amino terminus of the TnpA protein has 15.4% amino acid sequence identity with a corresponding domain for the putative transposase encoded by Lactococcus lactis insertion sequence S1 (ISS1). In addition, the sequence for the carboxyl-terminal 600 residues of the TnpA protein is 20.0% identical to that for the TniA transposase encoded by Tn5090 on Klebsiella aerogenes plasmid R751. The TnpA and TniA proteins contain the D,D(35)E motif characteristic of a recently defined superfamily consisting of bacterial transposases and integrase proteins of eukaryotic retroelements and retrotransposons. The two remaining ORFs on Tn5469 encode proteins of unknown function. Southern blot analysis showed that wild-type F. diplosiphon harbors five genomic copies of Tn5469. In comparison, mutant strain FdR1 harbors an extra genomic copy of Tn5469 which was localized to the inactivated rcaC gene. Among five morphologically distinct cyanobacterial strains examined, none was found to contain genomic sequences homologous to Tn5469.
从丝状蓝细菌双岐颤藻（Fremyella diplosiphon）的突变菌株FdR1中分离出一个转座子，命名为Tn5469，它插入到rcaC基因中。Tn5469是一个4904 bp的非复合转座子，具有25 bp近乎完美的末端反向重复序列，有三个串联排列、略有重叠的潜在开放阅读框（ORF），分别编码104.6 kDa（909个氨基酸残基）、42.5 kDa（375个氨基酸残基）和31.9 kDa（272个氨基酸残基）的蛋白质。Tn5469插入菌株FdR1的rcaC基因中产生了一个重复的5 bp靶序列。根据氨基酸序列鉴定，最大的ORF命名为tnpA，预计编码一种复合转座酶蛋白。TnpA蛋白氨基末端附近的一个230个氨基酸残基的结构域与乳酸乳球菌插入序列S1（ISS1）编码的假定转座酶的相应结构域有15.4%的氨基酸序列同一性。此外，TnpA蛋白羧基末端600个氨基酸残基的序列与产气克雷伯菌质粒R751上Tn5090编码的TniA转座酶的序列有同有20.0%的同一性。TnpA和TniA蛋白含有D,D(35)E基序，这是最近定义的一个超家族的特征基序，该超家族由细菌转座酶以及真核反转录元件和反转录转座子的整合酶蛋白组成。Tn5469上其余两个ORF编码功能未知的蛋白质。Southern杂交分析表明，野生型双岐颤藻含有5个Tn5469的基因组拷贝。相比之下，突变菌株FdR1含有一个额外的Tn5469基因组拷贝，该拷贝定位于失活的rcaC基因。在所检测的五个形态不同的蓝细菌菌株中，没有发现含有与Tn5469同源的基因组序列。
