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 N-terminal domain of L11/L12. The structure of the L11 N-terminal domain (NTD) consists of two helices packed against the concave surface of a three-stranded antiparallel beta sheet, with the first seven residues disordered. One of the most distinctive and conserved regions of the L11 molecule is the proline-rich helix 1, which appears to have a crucial functional role.

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. The N-terminal domain functions as a molecular switch, either by facilitating changes in the tertiary structure of the GAR/GAC (GTPase-associated region/centre) RNA or by controlling access to the RNA. In bacteria, the L11 N-terminal domain is post-translationally modified (trimethylated) at multiple residues by the S-adenosyl-L-methionine(AdoMet)-dependent trimethyltransferase PrmA.

PFAM:PF03946, INTERPRO:IPR036796,PMID:10338213,PMID:17215866,PMID:18611379,PMID:18406324