Figure 4

Consensus secondary structure model of the Oedogonium and Stigeoclonium psaC introns. The model is displayed according to Michel et al. [39]. Exon sequences are shown in lowercase letters. Positions exhibiting different nucleotides are denoted by dots. Positions showing deletions/additions are denoted by arrows labelled with two numbers; the left and right numbers refer to the nucleotides found in the Oedogonium and Stigeoclonium introns, respectively. Conserved base pairings are represented by dashes. Roman numerals specify the six major structural domains, whereas uppercase letters in bold denote the helices in domain I. Upper and lower numbers inside the variable loops indicate the sizes of these loops in the Oedogonium and Stigeoclonium introns, respectively. Tertiary interactions are represented by dashed lines, curved arrows, or Greek lettering. Nucleotides that potentially participate in the δ-δ' interaction are boxed. EBS and IBS are exon-binding and intron-binding sites, respectively. The putative site of lariat formation is denoted by an asterisk.