STRUCTURE AND FUNCTION OF TN5467, A TN21-LIKE TRANSPOSON LOCATED ON THE THIOBACILLUS-FERROOXIDANS BROAD-HOST-RANGE PLASMID PTF-FC2

A 3,5-kb region of plasmid pTF-FC2, which contains a transposon-like e lement designated Tn5467, has been sequenced, and its biological activ ity has been investigated. The transposon is bordered by two 38-bp inv erted repeat sequences which have sequence identity in 37 of 38 and in 38 of 39 bp to the tnpA distal and tnpA proximal inverted repeats of Tn21, respectively. Within these borders, open reading frames with ami no acid similarity to a glutaredoxin-like protein, a MerR regulatory p rotein, and a multidrug-resistant-membrane transport-like protein were found. The gene for the glutaredoxin-like protein was expressed in Es cherichia coli and enabled growth of a glutathione-requiring E. coli t rxA gshA mutant on minimal medium and the reduction of methionine sulf oxide to methionine. In addition, there were two regions which,,when t ranslated, had homology to 85% of the N-terminal region of the Tn21 re solvase (tnpR) and to 15% of the C terminus of the Tn21 transposase (t npA). A region containing res-like sites was located immediately upstr eam of the partial tnpR gene. Neither the partial transposase nor the resolvase genes of Tn5467 were biologically active, but Tn5467 was tra nsposed and resolved when the Tn21 transposase and resolvase were prov ided in trans. Tn5467 appears to be a defective transposon which belon gs to the Tn21 subgroup of the Tn3 family.