Ribosomal protein
Encyclopedia
A ribosomal protein is any of the protein
s 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. Most ribosomic proteins have been isolated and specific anti-bodies 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.
, S9, S12, S13, S16, S18, and S19 bind to the growing ribosome. These proteins also potentiate the addition of S2, S3, S10, S11, S14, and S21. Protein binding to helical junctions is important for initiating the correct tertiary fold of RNA and to organize the overall structure. Nearly all the proteins contain one or more globular domains. Moreover, nearly all contain long extensions that can contact the RNA in far-reaching regions. Additional stabilization results from the proteins' basic residues, as these neutralize the charge repulsion of the RNA backbone. Protein-protein interactions also exist to hold structure together by electrostatic and hydrogen bonding interactions. Theoretical investigations pointed to correlated effects of protein-binding onto binding affinities during the assembly process
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s that, in conjunction with rRNA
Ribosomal RNA
Ribosomal ribonucleic acid is the RNA component of the ribosome, the enzyme that is the site of protein synthesis in all living cells. Ribosomal RNA provides a mechanism for decoding mRNA into amino acids and interacts with tRNAs during translation by providing peptidyl transferase activity...
, make up the ribosomal
Ribosome
A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....
subunits involved in the cellular process of translation
Translation (genetics)
In molecular biology and genetics, translation is the third stage of protein biosynthesis . In translation, messenger RNA produced by transcription is decoded by the ribosome to produce a specific amino acid chain, or polypeptide, that will later fold into an active protein...
. A large part of the knowledge about these organic molecules has come from the study of E. coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
ribosomes. Most ribosomic proteins have been isolated and specific anti-bodies have been produced. These, together with electronic microscopy
Electron microscope
An electron microscope is a type of microscope that uses a beam of electrons to illuminate the specimen and produce a magnified image. Electron microscopes have a greater resolving power than a light-powered optical microscope, because electrons have wavelengths about 100,000 times shorter than...
and the use of certain reactives, have allowed for the determination of the topography of the proteins in the ribosome.
Proteins in E. coli ribosomes
The ribosome of E. coli has about 22 proteins in the small subunit (labelled S1 to S22) and 34 proteins in the large subunit (L1 to L36). All of them are different with three exceptions: one protein is found in both subunits (S20 and L26), L7 and L12 are acetylated and methylated forms of the same protein, and L8 is a complex of L7/L12 and L10. In addition, L31 is known to exist in two forms, the full length at 7.9 kilodaltons (kDa) and fragmented at 7.0 kDa. This is why the number of proteins in a ribosome is of 56. Except for S1 (with a molecular weight of 61.2 kDa), the other proteins range in weight between 4.4 and 29.7 kDa.Disposition in the small ribosomal subunit
In the small (30S) subunit of E. coli ribosomes, the proteins denoted S4, S7, S8, S15, S17, S20 bind independently to 16S rRNA. After assembly of these primary binding proteins, S5, S6Ribosomal protein s6
Ribosomal protein S6 is a component of the 40S ribosomal subunit and is therefore thought to be involved in regulating translation. Once thought to regulate the translation of 5' terminal oligopyrimidine RNA, this has since been disproven...
, S9, S12, S13, S16, S18, and S19 bind to the growing ribosome. These proteins also potentiate the addition of S2, S3, S10, S11, S14, and S21. Protein binding to helical junctions is important for initiating the correct tertiary fold of RNA and to organize the overall structure. Nearly all the proteins contain one or more globular domains. Moreover, nearly all contain long extensions that can contact the RNA in far-reaching regions. Additional stabilization results from the proteins' basic residues, as these neutralize the charge repulsion of the RNA backbone. Protein-protein interactions also exist to hold structure together by electrostatic and hydrogen bonding interactions. Theoretical investigations pointed to correlated effects of protein-binding onto binding affinities during the assembly process