An RNA-guided dsDNA endonuclease. When guided by an RNA derived from the right-end element of its insertion sequence element (IS), cleaves DNA downstream of the transposon-associated motif (TAM). Cleaves supercoiled and linear DNA in a staggered manner 15-21 bases from the TAM yielding 5'-overhangs. Binds reRNA, an approximately 150 nucleotide base sRNA derived from the 3' end of its own gene, the right end (RE) of the insertion sequence (IS) plus sequence downstream of the IS. Not required for transposition of the insertion element. The corresponding transposase in strains MG1655 and W3110 is a truncated pseudogene (yncK). In the N-terminal section; belongs to the transposase 2 family. In the C-terminal section; belongs to the transposase 35 family. It is uncertain whether Met-1 or Met-21 is the initiator; the sequence between Met-1 and Met-21 is conserved compared to orthologs but does not have a good ribosome-binding site (RBS) whereas Met-21 has a better RBS. Perhaps both are used, with translation initiating more often at the second Met. Truncated N-terminus.