Primary and secondary structure of the 18 S ribosomal RNA of the insect species Tenebrio molitor.

The sequence of the 18 S rRNA of Tenebrio molitor is reported. A detailed secondary structure model for eukaryotic small subunit rRNAs is proposed. The model comprises 48 universal helices that eukaryotic and prokaryotic small subunit rRNAs have in common, plus a number of helices in areas of variable secondary structure. For the central area of the model, an alternative structure is possible, applicable only to eukaryotic small subunit rRNAs. Possibly, small subunit rRNA switched to this alternative conformation after the eukaryotic branch had been established in evolution. Another possibility is that the two conformers represent a dynamic structural switch functioning during the translational activity of the eukaryotic ribosome.