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A ribosome is made from complexes of RNAs and proteins and is therefore a ribonucleoprotein complex. In prokaryotes each ribosome is composed of small (30S) and large (50S) components, called subunits, which are bound to each other: (30S) has mainly a decoding function and is also bound to the mRNA
The A-site (A for aminoacyl) of a ribosome is a binding site for charged t-RNA molecules during protein synthesis. [1] One of three such binding sites, the A-site is the first location the t-RNA binds during the protein synthesis process, the other two sites being P-site (peptidyl) and E-site (exit).
The ribosome catalyzes ester-amide exchange, transferring the C-terminus of a nascent peptide from a tRNA to the amine of an amino acid. These processes are able to occur due to sites within the ribosome in which these molecules can bind, formed by the rRNA stem-loops. A ribosome has three of these binding sites called the A, P and E sites:
50S, roughly equivalent to the 60S ribosomal subunit in eukaryotic cells, is the larger subunit of the 70S ribosome of prokaryotes. The 50S subunit is primarily composed of proteins but also contains single-stranded RNA known as ribosomal RNA (rRNA). rRNA forms secondary and tertiary structures to maintain the structure and carry out the catalytic functions of the ribosome.
Small subunit ribosomal ribonucleic acid (SSU rRNA) is the smaller of the two major RNA components of the ribosome. Associated with a number of ribosomal proteins, the SSU rRNA forms the small subunit of the ribosome. It is encoded by SSU-rDNA
The structural characterization of the eukaryotic ribosome [16] [17] [24] may enable the use of structure-based methods for the design of novel antibacterials, wherein differences between the eukaryotic and bacterial ribosomes can be exploited to improve the selectivity of drugs and therefore reduce adverse effects.
Ribosome biogenesis is a very tightly regulated process, and it is closely linked to other cellular activities like growth and division. [3] [4] Some have speculated that in the origin of life, ribosome biogenesis predates cells, and that genes and cells evolved to enhance the reproductive capacity of ribosomes. [5]
The ribosome of E. coli has about 22 proteins in the small subunit (labelled S1 to S22) and 33 proteins in the large subunit (somewhat counter-intuitively called L1 to L36). All of them are different with three exceptions: one protein is found in both subunits (S20 and L26), [ dubious – discuss ] L7 and L12 are acetylated and methylated forms ...