Ribosome inactivating protein
Encyclopedia
A ribosome inactivating protein is a protein synthesis inhibitor
that acts at the ribosome
..
A number of bacterial and plant toxins act by inhibiting protein synthesis in eukaryotic cells. The toxins of the Shiga
and ricin
family inactivate 60S ribosomal subunits by an N-glycosidic cleavage which releases a specific adenine
base from the sugar-phosphate backbone of 28S rRNA. Members of the family include shiga and shiga-like toxins, and type I (e.g. trichosanthin
and luffin) and type II (e.g. ricin
, agglutinin
and abrin
) ribosome inactivating proteins (RIPs). All these toxins are structurally related. RIPs have been of considerable interest because of their potential use, conjugated with monoclonal antibodies, as immunotoxin
s to treat cancer
s. Further, trichosanthin
has been shown to have potent activity against HIV-1-infected T cells and macrophages. Elucidation of the structure-function relationships of RIPs has therefore become a major research effort. It is now known that RIPs are structurally related. A conserved glutamic residue has been implicated in the catalytic mechanism; this lies near a conserved arginine, which also plays a role in catalysis.
Examples include:
They exist in bacteria and plants.
Protein synthesis inhibitor
A protein synthesis inhibitor is a substance that stops or slows the growth or proliferation of cells by disrupting the processes that lead directly to the generation of new proteins....
that acts at the ribosome
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....
..
A number of bacterial and plant toxins act by inhibiting protein synthesis in eukaryotic cells. The toxins of the Shiga
Shiga toxin
Shiga toxins are a family of related toxins with two major groups, Stx1 and Stx2, whose genes are considered to be part of the genome of lambdoid prophages. The toxins are named for Kiyoshi Shiga, who first described the bacterial origin of dysentery caused by Shigella dysenteriae. The most common...
and ricin
Ricin
Ricin , from the castor oil plant Ricinus communis, is a highly toxic, naturally occurring protein. A dose as small as a few grains of salt can kill an adult. The LD50 of ricin is around 22 micrograms per kilogram Ricin , from the castor oil plant Ricinus communis, is a highly toxic, naturally...
family inactivate 60S ribosomal subunits by an N-glycosidic cleavage which releases a specific adenine
Adenine
Adenine is a nucleobase with a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate and the cofactors nicotinamide adenine dinucleotide and flavin adenine dinucleotide , and protein synthesis, as a chemical component of DNA...
base from the sugar-phosphate backbone of 28S rRNA. Members of the family include shiga and shiga-like toxins, and type I (e.g. trichosanthin
Trichosanthin
Trichosanthin is a ribosome inactivating protein.It is derived from Trichosanthes kirilowii.It is also an abortifacient....
and luffin) and type II (e.g. ricin
Ricin
Ricin , from the castor oil plant Ricinus communis, is a highly toxic, naturally occurring protein. A dose as small as a few grains of salt can kill an adult. The LD50 of ricin is around 22 micrograms per kilogram Ricin , from the castor oil plant Ricinus communis, is a highly toxic, naturally...
, agglutinin
Agglutinin
An agglutinin is a substance that causes particles to coagulate to form a thickened mass . Agglutinins can be antibodies that cause antigens to aggregate by binding to the antigen-binding sites of antibodies. Agglutinins can also be any substance other than antibodies such as sugar-binding...
and abrin
Abrin
Abrin is a toxalbumin that is found in the seeds of a plant called lucky bean, rosary pea or jequirity pea. Abrin is similar to but far more deadly than ricin, a toxin found in the seeds of the castor oil plant.-Physical Properties:...
) ribosome inactivating proteins (RIPs). All these toxins are structurally related. RIPs have been of considerable interest because of their potential use, conjugated with monoclonal antibodies, as immunotoxin
Immunotoxin
An immunotoxin is a human-made protein that consists of a targeting portion linked to a toxin. When the protein binds to that cell, it is taken in through endocytosis, and the toxin kills the cell...
s to treat cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
s. Further, trichosanthin
Trichosanthin
Trichosanthin is a ribosome inactivating protein.It is derived from Trichosanthes kirilowii.It is also an abortifacient....
has been shown to have potent activity against HIV-1-infected T cells and macrophages. Elucidation of the structure-function relationships of RIPs has therefore become a major research effort. It is now known that RIPs are structurally related. A conserved glutamic residue has been implicated in the catalytic mechanism; this lies near a conserved arginine, which also plays a role in catalysis.
Examples include:
- TrichosanthinTrichosanthinTrichosanthin is a ribosome inactivating protein.It is derived from Trichosanthes kirilowii.It is also an abortifacient....
- RicinRicinRicin , from the castor oil plant Ricinus communis, is a highly toxic, naturally occurring protein. A dose as small as a few grains of salt can kill an adult. The LD50 of ricin is around 22 micrograms per kilogram Ricin , from the castor oil plant Ricinus communis, is a highly toxic, naturally...
- SaporinSaporinSaporin is a protein that is useful in biological research applications, especially studies of behavior. Saporin is a so-called ribosome inactivating protein , due to its N-glycosidase activity, from the seeds of Saponaria officinalis . It was first described by Fiorenzo Stirpe and his colleagues...
They exist in bacteria and plants.