Transposon Tn5090 of plasmid R751, which carries an integron, is related to Tn7, Mu, and the retroelements

Abstract

Integrons confer on bacterial plasmids a capability of taking up antibiotic resistance genes by integrasemediated recombination. We show here that integrons are situated on genetic elements flanked by 25-bp inverted repeats. The element carrying the integron of R751 has three segments conserved with similar elements in Tn2l and Tn5O86. Several characteristics suggest that this element is a transposon, which we call TnSO9O. TnS090 was shown to contain an operon with three open reading frames, of which two, tniA and tniB, were predicted by amino acid similarity to code for transposition proteins.

Non‐palindromic attI sites of integrons are capable of site‐specific recombination with one another and with secondary targets

“…4 and Table 1) but differ widely in their capability for fusion with R388⌬1. A new attI created by deletion of three mobile cassettes from the integron in R751 (Tn5090 ) (Rå dströ m et al, 1994;Recchia et al, 1995a) was unexpectedly one of the most efficient in the study.…”

“…1B;Rå dströ m et al, 1994;Paulsen et al, 1993). The aadA1 cassette of Tn21 with surrounding sequences including attI and attC was cloned in pSU18 to yield plasmid 2123.…”

Characterization of class I integrons in clinical strains of Salmonella enterica subsp. enterica serovars Typhimurium and Enteritidis from Norwegian hospitals

“…The disinfectant resistance gene qacE˜1 was absent in one S. Typhimurium isolate (1·5 %) and the sulphonamide resistance gene sulI was absent in seven S. Typhimurium isolates (10·6 %). Only one S. Typhimurium (1·5 %) isolate (2755/ 97) was positive for the tniA gene which has been associated with the In0, In2, In5 and Tn402(In16) integrons (Radstrom et al, 1994;Brown et al, 1996;Hall et al, 1994).…”

Complete transposition requires four active monomers in the mu transposase tetramer.

“…The similar effect of mutations, as well as amino acid se-Mu tiansposition lequires four active monomers quence similarity, argue that the essential acidic amino acids of MuA (D269 and E392) are analogs of those of the retroviral integrases (Baker and Luo 1994). Convincing D-D-35-E motifs have been detected in many transposi tion proteins, including those from Tn7, Tn552, IS3, and mariner elements (Fayet et al 1990;Rowland and Dyke 1990;Robertson 1993;Baker and Luo 1994;Radstrom et al 1994) and a related motif has been identified in the proteins encoded by excising elements from ciliated pro tozoa (Doak et al 1994). Thus, MuA appears to be a member of a large protein family that utilizes a similar constellation of residues to promote genetic recombina tion.…”