Segmentation pattern of ribosomes from Trypanosoma brucei, Leishmania donovani, and Trypanosoma cruzi. The LSU from these organisms is well known to be segmented in the characteristic eukaryotic 5.8S and six rRNA fragments; rRNA-α, srRNA-I, rRNA-β, srRNA-II, srRNA-III, and srRNA-IV. (A) 28S rRNA secondary structure from Saccharomyces cerevisiae, based on crystallographic structure data (Petrov et al. 2014), with the ribosomal segments from trypanosomatids drawn on top of it according to structural alignments (Supplemental Table S5). Color code is as follows: 5.8S is presented in blue, rRNA-α is in red, srRNA-I is in magenta, rRNA-β is in green, srRNA-II is in cyan, srRNA-III is in orange, and srRNA-IV is in purple; 5S rRNA is depicted in yellow in A and 18S is depicted in gray in B. Numbering system corresponds to S. cerevisiae. (B) Transcription unit from which the segmented ribosomes are originated. It starts with the 18S rRNA, followed by the 5.8S and the rest of the fragments in consecutive order when compared against unsegmented eukaryotic ribosomes.
