Large ribosomal subunit protein eL24-related, N-terminal (Ribosomal_eL24-rel_N)
Type: Domain

This entry represents a domain found N-terminal in large ribosomal subunit protein eL24 and related proteins.

A number of eukaryotic and archaeabacterial ribosomal proteins can be grouped on the basis of sequence similarities. One of these families consists of mammalian ribosomal protein eL24; yeast ribosomal protein eL24A/B;
Kluyveromyces lactis
ribosomal protein eL24;
Arabidopsis thaliana
ribosomal protein eL24y/z;
Haloarcula marismortui
ribosomal protein eL24; and
Methanocaldococcus jannaschii
protein eL24. These proteins have 60 to 160 amino-acid residues.

The crystal structure of the eL24 protein from Halobacterium marismortui (Haloarcula marismortui) has been determined . The protein is composed of a single structural domain which forms an α/β zinc-binding fold.

Ribosomal protein eL24/L24 is a ribosomal protein found in eukaryotes (L24) and in archaea (eL24, distinct from archaeal L24). eL24/L24 is located on the surface of the large subunit, adjacent to proteins L14 and L3, and near the translation factor binding site. eL24/L24 appears to play a role in the kinetics of peptide synthesis, and may be involved in interactions between the large and small subunits, either directly or through other factors. In mouse, a deletion mutation in L24 has been identified as the cause for the belly spot and tail (Bst) mutation that results in disrupted pigmentation, somitogenesis and retinal cell fate determination . L24 may be an important protein in eukaryotic reproduction: in shrimp, L24 expression is elevated in the ovary, suggesting a role in oogenesis , and in Arabidopsis, L24 has been proposed to have a specific function in gynoecium development .

Ribosomes are the particles that catalyse mRNA-directed protein synthesis in all organisms. The codons of the mRNA are exposed on the ribosome to allow tRNA binding. This leads to the incorporation of amino acids into the growing polypeptide chain in accordance with the genetic information. Incoming amino acid monomers enter the ribosomal A site in the form of aminoacyl-tRNAs complexed with elongation factor Tu (EF-Tu) and GTP. The growing polypeptide chain, situated in the P site as peptidyl-tRNA, is then transferred to aminoacyl-tRNA and the new peptidyl-tRNA, extended by one residue, is translocated to the P site with the aid the elongation factor G (EF-G) and GTP as the deacylated tRNA is released from the ribosome through one or more exit sites . About 2/3 of the mass of the ribosome consists of RNA and 1/3 of protein. The proteins are named in accordance with the subunit of the ribosome which they belong to the small (S1 to S31) and the large (L1 to L44). Usually they decorate the rRNA cores of the subunits.

Many ribosomal proteins, particularly those of the large subunit, are composed of a globular, surfaced-exposed domain with long finger-like projections that extend into the rRNA core to stabilise its structure. Most of the proteins interact with multiple RNA elements, often from different domains. In the large subunit, about 1/3 of the 23S rRNA nucleotides are at least in van der Waal's contact with protein, and L22 interacts with all six domains of the 23S rRNA. Proteins S4 and S7, which initiate assembly of the 16S rRNA, are located at junctions of five and four RNA helices, respectively. In this way proteins serve to organise and stabilise the rRNA tertiary structure. While the crucial activities of decoding and peptide transfer are RNA based, proteins play an active role in functions that may have evolved to streamline the process of protein synthesis. In addition to their function in the ribosome, many ribosomal proteins have some function 'outside' the ribosome .