Ribosomal protein S28e (IPR000289)
Short name: Ribosomal_S28e
Overlapping homologous superfamilies
- Nucleic acid-binding, OB-fold (IPR012340)
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 [PMID: 11297922, PMID: 11290319]. 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 [PMID: 11290319, PMID: 11114498].
A number of eukaryotic and archaebacterial ribosomal proteins can be grouped on the basis of sequence similarities. Examples are:
- Mammalian S28 [PMID: 11875025]
- Plant S28 [PMID: 8278557]
- Fungi S33 [PMID: 1481571]
- Archaebacterial S28e.
These proteins have from 64 to 78 amino acids and a highly conserved C-terminal region.
S1-like RNA-binding domains are found in a wide variety of RNA-associated proteins. S28E protein is a component of the 30S ribosomal subunit. S28E is highly conserved among archaea and eukaryotes. S28E may control precursor RNA splicing and turnover in mRNA maturation process but its function in the ribosome is largely unknown. The structure contains an OB-fold found in many oligosaccharide and nucleic acid binding proteins. This implies that S28E might be involved in protein synthesis [PMID: 14627743, PMID: 14627742, PMID: 9008164].