This superfamily entry represents the C-terminal domain of the ribosomal protein L9 found in the large subunit of the ribosome. This entry includes homologues of L9. The N-terminal domain is included in superfamily 3.40.5.10. The C-terminal domain consists of two loops, an alpha-helix and a three-stranded mixed parallel, anti-parallel beta-sheet packed against the central alpha-helix.

L9 comprises two separated globular domains connected by a rigid linker, an exposed alpha-helix, as described in Bacillus stearothermophilus. Each domain contains an rRNA binding site (for 23S rRNA), and both present well-conserved positively charged and aromatic amino acid residues on the surface. The long central alpha-helix varies in length across species and is suggested to have an architectural role in the separation of the N-terminal and C-terminal domains.

PFAM:PF03948, INTERPRO:IPR036791,PMID:8306963