The Ribosome
| Prokaryotic Translation | Table of Contents |
The ribosome is a large complex composed of a number of protein subunits and several RNA molecules that are called ribosomal RNAs or rRNAs.
The Prokaryotic Ribosome
The prokaryotic ribosome is referred to as the 70S ribosome. The S is a symbol for a sedimentation coefficient called the Svedborg unit, which is a measure of molecular size as determined by the rate of sedimentation under certain conditions during centrifugation. The 70S ribosome is itself composed of two subunits, the Large 50S subunit and the Small 30S subunit (sedimentation coefficients are not additive).
Large subunit: The large subunit is composed of 31 proteins that are called Large Ribosomal Subunit Proteins (sometimes designated rpl for ribosomal protein, large subunit). In addition there is a 23S rRNA and a 5S rRNA.
Small subunit: The large subunit is composed of 21 proteins that are called Small Ribosomal Subunit Proteins (sometimes designated rps for ribosomal protein, small subunit). In addition there is the 16S rRNA.
The Eukaryotic Ribosome
The eukaryotic ribosome is referred to as the 80S ribosome. The 80S ribosome is itself composed of two subunits, the Large 60S subunit and the Small 40S subunit.
Large subunit: The large subunit of the 80S ribosome is composed of 49 proteins, a 28S rRNA, a 5.8S rRNA and a 5S rRNA.
Small subunit: The large subunit of the 80S ribosome is composed of 33 proteins and the 18S rRNA.
| Prokaryotic Translation | Table of Contents |