Ribosomal RNA expansion segments in the yeast large ribosomal subunit. (A) Secondary structure of Saccharomyces cerevisiae large subunit ribosomal RNA (rRNA). Different domains are marked by different colors. The ES deletions studied here (14 of the 16 ES in yeast LSU rRNA) are highlighted by maroon circles and labeled. (B) Pymol representation of the large subunit rRNA. ES deletions studied are highlighted in maroon as in A and labeled. The peptidyl transferase center (PTC) is shown in cyan. (C) ES progressively increase in size and complexity in eukaryotes. Helix 25 (h25) is shown as an example to demonstrate the increase in sequence length (not to scale) and the number of helical branches of ES7L, from E. coli through Homo sapiens.
