Transposition and transposition immunity of transposon Tn3 derivatives having different ends.

Novel Tn1/3 derivatives that contained either two left- or two
right-hand ends of the transposon were constructed in a small
plasmid. Both transposed at reasonable frequencies to give
nonnal transposition products, suggesting that only the 38-bp
inverted repeats of Tn3 are essential for transposition. Plasmids
containing transposon derivatives with only one end
(either left or right) undergo transposase-dependent transposition
between replicons at much lower frequencies, resulting
in co-integrate molecules in which there is no substantial
duplication of transposon DNA and that appear to be simple
fusions of the two plasmids. Both the right and left halves of
the transposon are separately able to confer transposition
immunity to the plasmid, this immunity being inseparably
linked to transposition proficiency and specificity.