Ribosomal particles are denoted according to their
sedimentation coefficients in
Svedberg units. The 60S subunit is the large subunit of
eukaryotic 80S ribosomes. It is structurally and functionally related to the
50S subunit of
70S prokaryotic ribosomes.
However, the 60S subunit is much larger than the prokaryotic 50S subunit and contains many additional protein segments, as well as
ribosomal RNA
Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from riboso ...
expansion segments.
Overall structure
Characteristic features of the large subunit, shown below in the "Crown View", include the central protuberance (CP) and the two stalks, which are named according to their bacterial protein components (L1 stalk on the left as seen from the subunit interface and L7/L12 on the right). There are three binding sites for
tRNA
Transfer RNA (abbreviated tRNA and formerly referred to as sRNA, for soluble RNA) is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length (in eukaryotes), that serves as the physical link between the mRNA and the amino ...
, the A-site, P-site and E-site (see article on
protein translation
In molecular biology and genetics, translation is the process in which ribosomes in the cytoplasm or endoplasmic reticulum synthesize proteins after the process of transcription of DNA to RNA in the cell's nucleus. The entire process ...
for details).
The core of the 60S subunit is formed by the
28S ribosomal RNA
28S ribosomal RNA is the structural ribosomal RNA (rRNA) for the large subunit (LSU) of eukaryotic cytoplasmic ribosomes, and thus one of the basic components of all eukaryotic cells. It has a size of 25S in plants and 28S in mammals, hence th ...
(abbreviated 28S rRNA), which is homologous to the prokaryotic
23S rRNA, which also contributes the active site (
peptidyl transferase
The peptidyl transferase is an aminoacyltransferase () as well as the primary enzymatic function of the ribosome, which forms peptide bonds between adjacent amino acids using tRNAs during the translation process of protein biosynthesis. The subs ...
center, PTC) of the ribosome.
The rRNA core is decorated with dozens of proteins. 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. Proteins shared only between eukaryotes and archaea are shown as orange ribbons and proteins specific to eukaryotes are shown as red ribbons.
60S ribosomal proteins
The table "60S ribosomal proteins" shows the individual protein folds of the 60S subunit colored by conservation as above. The eukaryote-specific extensions, ranging from a few residues or loops to very long alpha helices and additional domains, are highlighted in red.
Historically, different nomenclatures have been used for ribosomal proteins. For instance, proteins have been numbered according to their migration properties in
gel electrophoresis
Gel electrophoresis is a method for separation and analysis of biomacromolecules ( DNA, RNA, proteins, etc.) and their fragments, based on their size and charge. It is used in clinical chemistry to separate proteins by charge or size (IEF ...
experiments. Therefore, different names may refer to homologous proteins from different organisms, while identical names do not necessarily denote homologous proteins. The table "60S ribosomal proteins" cross-references the human ribosomal protein names with yeast, bacterial, and archaeal homologs.
Further information can be found in the
ribosomal protein gene database (RPG).
See also
*
Eukaryotic small ribosomal subunit (40S)
The eukaryotic small ribosomal subunit (40S) is the smaller subunit of the eukaryotic 80S ribosomes, with the other major component being the large ribosomal subunit (60S). The "40S" and "60S" names originate from the convention that ribosomal pa ...
References
External links
Ribosomal Protein Gene Database (RPG)
{{Ribosome subunits
Ribosomal RNA