FIG. 1.

Organization of a typical IS. The IS is represented as an open box in which the terminal IRs are shown as grey boxes labelled IRL (left inverted repeat) and IRR (right inverted repeat). A single open reading frame encoding the transposase is indicated as a hatched box stretching along the entire length of the IS and extending within the IRR sequence. XYZ enclosed in a pointed box flanking the IS represents short DR sequences generated in the target DNA as a consequence of insertion. The Tpase promoter, p, which is partially localized in IRL, is shown by a horizontal arrow. A typical domain structure (grey boxes) of the IRs is indicated beneath. Domain I represents the terminal base pairs at the very tip of the element whose recognition is required for Tpase-mediated cleavage. Domain II represents the base pairs necessary for sequence-specific recognition and binding by the Tpase.