Close-up views of the (A) H54 region showing that the steeple (deep pink) emerges from H54, (B) H14 and H16 region displaying that the bifurcated density (orange) is related to these helices, and (C) H31 region identifying the density corresponding to the extra helix (purple), H31a, in the 23S rRNA, are shown in stereo. Density clusters attributable to extra domains of M. smegmatis ribosomal large subunit proteins L4/L17/L22/L29 (D), and L25 (E) are also shown in stereo. T. thermophilus L25 (from pdb code 2J01, chain Z, 3–179 amino acids) protein structure is shown here (magenta) to identify the C-terminal domain. Part of the C-terminal extra domain overlaps with the density cluster attributed to L25 in Msm70S.