RICI_RICCO
Domain
Ricin B chain
Composed of two domains, each domain consists of 3 homologous subdomains (alpha, beta, gamma).
Function
Ricin is highly toxic to animal cells, and to a lesser extent to plant cells.
Ricin 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. Can inactivate a few thousand ribosomes per minute, faster than the cell can make new ones. Therefore a single molecule can kill an animal cell.
Ricin 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. Also responsible for cell agglutination (Lectin activity).
Sequence Similarities
In the N-terminal section; belongs to the ribosome-inactivating protein family. Type 2 RIP subfamily.
Alternative names
Ricin