Ricin chain A (RTA) is a ribosome inactivating enzyme with a molecular weight of 32 kDa. RTA is normally linked by a disulfide bond to the galactose/N acetylgalactosamine binding lectin (34 kDa), also called the B chain or RTB. Together with RTB, RTA constitutes the heterodimeric cytotoxin Ricin (RCA 60) from Ricinus communis. This ricin, which is a type 2 RIP (ribosome inactivating protein) is among the most potent cytotoxins in nature. Ricin is highly toxic to animal cells and to a lesser extent to plant cells.
Function:
Ricin is highly toxic to animal cells and to a lesser extent to plant cells. The A chain acts as a glycosidase that removes a specific adenine residue from an exposed loop of the 28S rRNA (A4324 in mammals), leading to rRNA breakage. As this loop is involved in elongation factor binding, modified ribosomes are catalytically inactive and unable to support protein synthesis. The A chain can inactivate a few thousand ribosomes per minute, faster than the cell can make new ones. Therefore a single A chain molecule can kill an animal cell. The B chain binds to beta-D-galactopyranoside moieties on cell surface glycoproteins and glycolipids and facilitates the entry into the cell of the A chain; B chains are also responsible for cell agglutination (Lectin activity).
Subunit:
In the N-terminal section; belongs to the ribosome-inactivating protein family. Type 2 RIP subfamily.CuratedContains 2 ricin B-type lectin domains.
SWISS:
P02879
Gene ID:
8287993
Database links:
Entrez Gene: 8287993 Ricinus communis
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