Additional Watson-Crick interactions suggest a structural core in large subunit ribosomal RNA

Two new Watson-Crick type interactions in 23S-like ribosomal RNA have been identified by comparative sequence analysis. These interactions, A1269/U2011 and C1270/G2010 (E. coli numbering) along with the previously proposed A1262/U2017 suggest an anti-parallel helical arrangement characteristic of secondary structure in the 1265/2015 region of 23S rRNA. Nested within these three interactions are three universal juxtapositions which in principle allow the formation of an irregular helix containing two additional A-G interactions and a universal A-U pair. Whether or not this extended helix is biologically significant is uncertain. The proponderance of interactions in the 1265/2015 region and its location relative to the known structural domains of 23S rRNA suggest that this region may be part of a central structural core similar to that already known in 16S rRNA.