The Nucleotide Sequence and Protein-coding Capability of the Transposable Element IS5

The nucleotide sequence of IS5, a bacterial insertion sequence, has been determined. It is 1195 bp long and contains an inverted terminal repetition of 16 bp with one mismatch. One open reading frame, spanning nearly the entire length of the element, could encode a polypeptide of 338 amino acids. Upon insertion into a DNA segment, IS5 causes a duplication of 4 bp. Based on seven examples, this site of insertion appears to be nonrandom, and the consensus target site sequence is C . T/A . A . G/A (or C/T . T . A/T . G on the opposite strand). The nucleotide sequences of IS5 insertions into the B and cim genes of bacteriophage Mu have allowed tentative identification of the protein-coding frames of B and cim.