Transposition of a DNA fragment flanked by two inverted Tn1 sequences

The 32 Md fragment (derived from plasmid RP4::Tn1) carrying the Kmr gene and flanked by two inverted Tn1 elements is capable of recA-independent translocation to other plasmids. We designated this new transposon Tn1755. In various crosses, frequencies of Tn1755 transposition to plasmids Co1B-R3, R15 and F'Co1VBtrp varied from 2.5 to 90% of the frequencies of Tn1 transposition. Tn1755 can integrate into various sites of the recipient plasmids. We failed to observe transposition of another RP4::Tn1 fragment flanked by two opposingly oriented Tn1 transposons and harboring the Tcr gene. Presumably, to form a new transposable structure, other features must also be of importance.