The N-terminal domain of the insertion sequence 30 transposase interacts specifically with the terminal inverted repeats of the element.

The gene for the insertion sequence (IS) 30 transposase is placed under the control of the tac promoter, and large quantities of transposase are expressed upon induction. The resulting protein precipitates inside the Escherichia coli cells in the form of inclusion bodies which, upon cell lysis, cannot be dissolved under nondenaturing conditions. In contrast, the N-terminal third of the transposase, a 17-kDa protein produced by a truncated gene, can be purified and is able to interact site specifically with the ends of the IS30 element. In DNase I footprint experiments, regions of 26 nucleotides on one DNA strand and 19 nucleotides on the other strand at either end of the element are protected from nuclease digestion. It is concluded that a functional DNA-binding domain can be formed by expression of only one-third of the complete IS30 transposase. Sequence comparison shows a homology of the IS30 ends to the ends of IS4351 and to the L1 end of bacteriophage Mu.