This superfamily includes the ribosomal protein L11 found in the large (50S) ribosomal subunit, including homologues from other organisms such as bacteria, plant chloroplast, red algal chloroplast, cyanelle and archaeabacterial. The mammalian, plant and yeast homologues are known as L12 (in yeast, YL15).

L11 consists of a 23S rRNA binding C-terminal domain and an N-terminal domain that directly contacts protein synthesis factors. These two domains are joined by a flexible linker that allows inter-domain movement during protein synthesis. This entry represents the C-terminal domain of L11/L12. The domain consists of a three-helical bundle and a short parallel two-stranded beta-ribbon, with an overall alpha3-beta4-alpha4-alpha5-beta5 topology. All five secondary structure elements contribute to a conserved hydrophobic core. The domain is characterised by two extended loops that are disordered in the absence of the RNA but have defined structures in the complex.

L11 is known to bind directly to the 23S rRNA and plays a significant role during initiation, elongation, and termination of protein synthesis. While the C-terminal domain of L11 binds RNA tightly, the N-terminal domain makes only limited contacts with RNA and is proposed to function as a switch that reversibly associates with an adjacent region of RNA. In E. coli, the C-terminal half of L11 has been shown to be in an extended and loosely folded conformation and is likely to be buried within the ribosomal structure.

PFAM:PF00298, INTERPRO:IPR036769,PMID:10338213,PMID:17215866,PMID:18611379,PMID:18406324