Tn5041: a chimeric mercury resistance transposon closely related to the toluene degradative transposon Tn4651

Abstract

This paper reports the discovery and characterization of Tn5041, a novel-type transposon vehicle for dissemination of mercury resistance in natural bacterial populations. Tn5041 (14876 bp), identified in a Pseudomonas strain from a mercury mine, is a Tn3 family mercury resistance transposon far outside the Tn21 subgroup. As in other Tn3 family transposons, Tn5041 duplicates 5 bp of the target sequence following insertion. Tn5041 apparently acquired its mer operon as a single-ended relic of a transposon belonging to the classical mercury resistance transposons of the Tn27 subgroup. The putative transposase and the 47 bp terminal inverted repeats of Tn5041 are closely related to those of the toluene degradative transposon Tn4651 and fall into a distinct subgroup on the fringe of the Tn3 family. The amino acid sequence of the putative resolvase of Tn5041 resembles site-specif ic recombinases of the integrase family. Besides the mer operon and putative transposition genes, Tn5041 contains a 4 kb region that accommodates a number of apparently defective genes and mobile elements.

Genetic Environments of the rmtA Gene in Pseudomonas aeruginosa Clinical Isolates

“…Tn5041 was previously identified in a strain of a Pseudomonas species as a mercury resistance transposon (3,16). Tn5041 carries a 4-kbp insert of unknown origin between orfQ and the mer operon, and several nonfunctional pseudogenes and possible mobile elements such as the ␥ element locate in this region.…”

Characterization of a marine-isolated mercury-resistant Pseudomonas putida strain SP1 and its potential application in marine mercury reduction

“…Cloning and localization of the mer operon Three pairs of primers (merF1 and merR2, merF2 and merR3, and merCF1 and merR4) listed in Table 1 were designed according to the mer sequence of mercuryresistant Pseudomonas/Xanthomonas strains isolated from a mercury mine in Kirgizia, Central Asia, submitted to the National Center for Biotechnology Information (NCBI) under the accession number X98999 reported by Kholodii et al (1997). PCR products were separated, purified, and then ligated into pMD18-T. E. coli transformants were selected and sequencing of the DNA fragment was carried out.…”

Site-Specific Recombination System Encoded by Toluene Catabolic Transposon Tn4651

“…4). In contrast, TnpT showed 29% identity and 47% similarity only with the OrfQ protein of Tn5041 (X98999) (17).…”

“…(13,35) and the related transposon Tn5041 (17). The following abbreviations and symbols are used: xyl, toluene-degrading genes; U, upper pathway operon; M, meta pathway operon; mer, genes for resistance to mercuric ion; TnpC, a regulator that controls negatively the TnpA expression at the posttranscriptional level (13); filled arrowhead, IR; and open arrowhead, IS1246 (26).…”

“…1B). BLAST searches revealed that TnpS had homology with the integrase family of site-specific recombinases (23), showing 36 to 38% identity and 53 to 55% similarity with the putative integrase from the atrazine catabolic plasmid pADP-1 of a Pseudomonas strain (U66917) (22), the integrase-like protein from Coxiella burnetii (Y15898), and the OrfI protein of Tn5041 (X98999) (17). The proteins in this family invariably have the conserved R-H-R-Y tetrad in domains I and II with proper spacing (23), and these structural characteristics were also found in TnpS (Fig.…”