Figure 2

Consensus structure diagram of the Nae.S516 twin-ribozyme intron. The structure diagram is based on the 13 completely sequenced Nae.S516 introns from distinct natural isolates (see Table 1) and is folded according to previously reported models [7,19] with some modifications. Invariant nucleotide residues are presented as uppercase letters. Red filled circles represents a variable position in one or more intron sequences, and regions with size and structural variations are boxed. Nae.S516 contains the two distinct ribozymes NaGIR1 and NaGIR2, and the homing endonuclease gene NaHEG. IPS, internal processing site; BP, branch point nucleotide (U).