Putative secondary structures of the group I intron RNAs.

<p><b>A.</b> Secondary structure of the <i>Leucocryptos cob</i> intron. Putative Watson–Crick and wobble base pairs are shown by lines and open circles, respectively. Capital and small letters represent intron and exon nucleotides, respectively. Double helical structures, which are characteristic to group I introns, are labeled as P1–P10. The open reading frame (ORF) for a LAGLIDADG-type homing endonuclease (closed box; 217 amino acid residues) was found in the 718 nucleotide-long loop region between P1 and P2. <b>B.</b> Secondary structure of the <i>Leucocryptos cox1</i> intron. The details of this figure are same as described in A, except the ORF for a LAGLIDADG-type homing endonuclease (closed box; 267 amino acid residues) was found in the 827 nucleotide-long loop region between P1 and P10. P9.1 and P7.1, which are absent in the <i>Leucocryptos cob</i> intron, are shaded.