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Specificity
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Recognizes the B chain of the ricin toxin (RCA60), a 60kD glycoprotein. The ricin toxin consists of two chains, A and B, covalently linked by a disulfide bond. The A chain acts as a glycosidase that removes an adenine residue from the 28S rRNA. The area from which the adenine is removed is essential for binding of elongation factors, destroying it leaves the ribosome inactive and unable to support protein synthesis. The A chain can inactivate a few thousand ribosomes per minute, much faster than the cell can replace them, meaning that a single ricin A chain can kill a cell. The B chain binds to complex carbohydrates on the cell surface to facilitate entry of the A chain into the cell. Without the B chain, the A chain has very low toxicity. Ricin is easily extracted from the castor bean (Ricinus communis), and the lethal dose for humans is very small. It is toxic when inhaled, ingested or injected and there is no known antidote, although a vaccine has been developed. Treatment is symptomatic and supportive, with long term organ damage likely in survivors. The ease of extraction and distribution makes it a potential candidate for biological warfare although it is less stable than other agents, such as anthrax. Recognizes the B chain of the ricin toxin (RCA60) Recognizes the agglutinin RCA120. May be used to detect ricin in ELISA assays.
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