Polysome
Encyclopedia
Polyribosomes also known as ergosomes are a cluster of ribosome
s, bound to a mRNA molecule, first discovered and characterized by Jonathan Warner, Paul Knopf, and Alex Rich in 1963. Many ribosomes read one mRNA simultaneously, progressing along the mRNA to synthesize
the same protein. They may appear as clusters, linear polysomes, or circular rosettes on microscopy, but mainly circular in vivo. This circularization is aided by the fact that mRNA is able to be twisted into a circular formation, creating a cycle of rapid ribosome recycling, and utilization of ribosomes.
The 5' 7-methylguanosine cap
and 3' poly(A)
tail present on eukaryotic mRNA aid in this process.
Polyribosomes can be found in three forms: free, cytoskeletal bound, and membrane bound
.
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....
s, bound to a mRNA molecule, first discovered and characterized by Jonathan Warner, Paul Knopf, and Alex Rich in 1963. Many ribosomes read one mRNA simultaneously, progressing along the mRNA to synthesize
Protein biosynthesis
Protein biosynthesis is the process in which cells build or manufacture proteins. The term is sometimes used to refer only to protein translation but more often it refers to a multi-step process, beginning with amino acid synthesis and transcription of nuclear DNA into messenger RNA, which is then...
the same protein. They may appear as clusters, linear polysomes, or circular rosettes on microscopy, but mainly circular in vivo. This circularization is aided by the fact that mRNA is able to be twisted into a circular formation, creating a cycle of rapid ribosome recycling, and utilization of ribosomes.
The 5' 7-methylguanosine cap
5' cap
The 5' cap is a specially altered nucleotide on the 5' end of precursor messenger RNA and some other primary RNA transcripts as found in eukaryotes. The process of 5' capping is vital to creating mature messenger RNA, which is then able to undergo translation...
and 3' poly(A)
Polyadenylation
Polyadenylation is the addition of a poly tail to an RNA molecule. The poly tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature messenger RNA for translation...
tail present on eukaryotic mRNA aid in this process.
Polyribosomes can be found in three forms: free, cytoskeletal bound, and membrane bound
Membrane bound polyribosome
Membrane bound polyribosomes are attached to a cell's endoplasmic reticulum. When certain proteins are synthesized by a ribosome they can become "membrane-bound". The newly produced polypeptide chains are inserted directly into the endoplasmic reticulum by the ribosome and are then transported to...
.