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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:
The complete structure of the eukaryotic 80S ribosome from the yeast Saccharomyces cerevisiae was obtained by crystallography at 3.0 A resolution. [18] These structures reveal the precise architecture of eukaryote-specific elements, their interaction with the universally conserved core, and all eukaryote-specific bridges between the two ...
Ribosomes are the macromolecular machines that are responsible for mRNA translation into proteins. The eukaryotic ribosome, also called the 80S ribosome, is made up of two subunits – the large 60S subunit (which contains the 25S [in plants] or 28S [in mammals], 5.8S, and 5S rRNA and 46 ribosomal proteins) and a small 40S subunit (which contains the 18S rRNA and 33 ribosomal proteins). [6]
The differences in structure allow some antibiotics to kill bacteria by inhibiting their ribosomes while leaving human ribosomes unaffected. In all species, more than one ribosome may move along a single mRNA chain at one time (as a polysome ), each "reading" a specific sequence and producing a corresponding protein molecule.
However, 23S rRNA positions (G2252, A2451, U2506, and U2585) have a significant function for tRNA binding in the P site of the large ribosomal subunit. [7] These modification nucleotides in site P can inhibit peptidyl-tRNA from binding. U2555 modification can also intervene with transferring peptidyl-tRNA to puromycin.
In the figure "Crystal Structure of the Eukaryotic 60S Ribosomal Subunit from T. thermophila", the ribosomal RNA core is represented as a grey tube and expansion segments are shown in red. Proteins which have homologs in eukaryotes, archaea and bacteria are shown as blue ribbons.
The ribosomal DNA includes all genes coding for the non-coding structural ribosomal RNA molecules. Across all domains of life, these are the structural sequences of the small subunit (16S or 18S rRNA) and the large subunit (23S or 28S rRNA).
After assembly of these primary binding proteins, uS5, bS6, uS9, uS12, uS13, bS16, bS18, and uS19 bind to the growing ribosome. These proteins also potentiate the addition of uS2, uS3, uS10, uS11, uS14, and bS21. Protein binding to helical junctions is important for initiating the correct tertiary fold of RNA and to organize the overall structure.