Ribosomal protein
| Mitochondrial ribosomal protein L31 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | L31 | ||||||||
| Pfam | PF09784 | ||||||||
| InterPro | IPR016340 | ||||||||
| PROSITE | PDOC00880 | ||||||||
| SCOP | 1m90 | ||||||||
| SUPERFAMILY | 1m90 | ||||||||
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| Available protein structures: | |
|---|---|
| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
A ribosomal protein is any of the proteins that, in conjunction with rRNA, make up the ribosomal subunits involved in the cellular process of translation. A large part of the knowledge about these organic molecules has come from the study of E. coli ribosomes. All ribosomal proteins have been isolated and many specific antibodies have been produced. These, together with electronic microscopy and the use of certain reactives, have allowed for the determination of the topography of the proteins in the ribosome. E.coli, other bacteria and Archaea have a 30S small subunit and a 50S large subunit, whereas humans and yeasts have a 40S small subunit and a 60S large subunit. Equivalent subunits are frequently numbered differently between bacteria, Archaea, yeasts and humans. More recently, a near-complete (near)atomic picture of the ribosomal proteins is emerging from the latest high-resolution cryo-EM data (including PDB ID: 5AFI).
Ribosomal proteins are among the most highly conserved proteins across all life forms. Among the 40 proteins found in various small ribosomal subunits, 15 subunits are universally conserved across prokaryotes and eukaryotes. However, 7 subunits are only found in bacteria (S21, S6, S16, S18, S20, S21, and THX), while 17 subunits are only found in archea and eukaryotes. Typically 22 proteins are found in bacterial 30S subunits and 32 in yeast, human and most likely most other eukaryotic species. Twenty-seven (out of 32) proteins of the eukaryotic small ribosomal subunit proteins are also present in archaea (no ribosomal subunit is exclusively found in archaea), confirming that they are more closely related to eukaryotes than to eubacteria.
Among the large ribosomal subunit, 18 proteins are universal, i.e. found in both bacteria, eukaryotes, and archea. 14 proteins are only found in bacteria, while 27 proteins are only found in archea and eukaryotes. Again, archea have no proteins unique to them
Despite their high conservation over billions of years of evolution, the absence of several ribosomal proteins in certain species shows that ribosomal subunits have been added and lost over the course of evolution. This is also reflected by the fact that several ribosomal proteins do not appear to be essential when deleted. For instance, in E. coli nine ribosomal proteins (L15, L21, L24, L27, L29, L30, L34, S9, and S17) are nonessential for survival when deleted. Taken together with previous results, 22 of the 54 E. coli ribosomal protein genes can be individually deleted from the genome. Similarly, 16 ribosomal proteins (L1, L9, L15, L22, L23, L28, L29, L32, L33.1, L33.2, L34, L35, L36, S6, S20, and S21) were successfully deleted in Bacillus subtilis. In conjunction with previous reports, 22 ribosomal proteins have been shown to be nonessential in B. subtilis, at least for cell proliferation.
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