Structure of the T. vaginalis MULEs. Putative terminal inverted repeats (TIRs) are denoted by black arrowheads at each end of the elements. Bases that are variable between TIRs are in lowercase type. Dark gray boxes represent internal non-coding sequences. The internal region of each element (clear gray box) corresponds to an ORF that encodes putative MULEs-related transposase domains. Location of a transposase zinc finger (double black lines) is also shown.