Castor-bean lectin

Harley SM and Lord JM (1985). In vitro endopro-teolytic cleavage of castor bean lectin precursors. Plant Sci, 41, 111-116. 

Castor bean lectins RCAgo 60000 D-GalNAc 50 mM GalNAc... 

Not all preparations of a-L-iduronidase function as a corrective factor for Hurler s syndrome. Corrective and non-corrective forms of the enzyme in urine have been separated by affinity chromatography on heparin immobilized on agarose whereas they have similar catalytic properties, they differ in molecular weight (8.7 x lOS 6.7 x 10 ) and in binding to an immobilized castor-bean lectin. The corrective form was the only one efficiently taken up by Hurler s fibroblasts. 

Lectin toxicity - nausea, diarrhea, headache, confusion, dehydration, death Wisteria, castor bean (Ricinus communis) Lectins bind to cell surfaces Ricin - blocks protein synthesis, very toxic, 5 to 6 beans can kill a child... 

Other approaches to induce gastrointestinal discomfort have far more serious toxic effects. The chemical colchicine stops cell division (an antimitotic), producing severe nausea, vomiting, and dehydration, which can lead to delirium, neuropathy, and kidney failure. On the other hand, colchicine is used in the treatment of gout and has been studied as an anticancer agent because it stops cell division. Most toxic of all are plants that produce lectins, and the most toxic of these is the chemical ricin produced by castor beans. Only 5 to 6 seeds are necessary to kill a small child. Fortunately, following oral consumption much of the ricin is destroyed in the stomach. Ricin is extremely effective at stopping protein synthesis, so much so that direct exposure to only 0.1 pg/kg can be fatal. 

Ricin was found by Stillmark in 1889 as the first plant lectin derived from the seeds of the castor plant, Ricinus communis L., a member of the Euphorbiaceae or spurge family. Other members of this family include the popular houseplants poinsettia E. pulcherrima), and the croton species. The term castor bean is used commonly to refer to both the plant and seed of R. communis. Ricinus communis commonly grows along streams and riverbeds in addition to subtropical locations high in nutrients. Ricinus communis is a coarse perennial, 10-13 m tall in the tropics, with a stem 7.5-15 cm... 

Some of the proteins are toxic in nature. Ricin present in castor bean is extremely toxic to higher animals in very small amounts. Enzyme irvhibitors such as trypsin inhibitor bind to digestive enzyme and prevent the availability of the protein. Lectin, a toxic protein present commonly in legumes, agglutinates red blood cells. A bacterial toxin causes cholera, which is a protein. Snake venom is protein in nature. 

Chemical Abstracts Service Registry Number CAS 1393-62-0. Abrin is a toxalbumin similar in structure, absorption, and mechanism of action to ricin but is found not in castor beans but rather in jequirity beans. No reports of its use as a battlefield or terrorist agent exist, but in mice it is 75 times more potent than ricin. No specific treatment is available. Both ricin and abrin are type 2 ribosomal inhibitory proteins (RIPs) the other potent toxins in this class are Eranthis hyemalis lectin (EHL) from winter aconite, modeccin and volkensin from African succulents, and viscumin from mistletoe. 

A group of plant lectins, such as abrin, ricin, and mod-eccin, are highly toxic to eukaryotic cells. Their mode of action consists of inhibition of protein synthesis by enzymatically inactivating the EF-2 binding region of the 60S ribosomal subunit, whereas the diphtheria toxin inactivates the EF-2 protein itself. Ricin is isolated from castor beans and has a molecular weight of 66,000. Like most plant and bacterial toxic proteins, ricin contains two... 

As an additional source of complexity, the ricin gene is part of a multigene family within the castor bean plant that encodes for the production of pro-ricin (the natural ricin precursor), several apparently inactive polypeptides, and a well-studied, structurally related lectin called R. communis agglutinin I (RCA120) (Tregear and Roberts, 1992 Pinkerton et al., 1999 Helmy and Pieroni, 2000). 

Lord JM (1985b). Synthesis and intracellular transport of lectin and storage protein precursors in endosperm from castor bean. Eur J Biochem, 146, 403-409. 

The synthesis of ricin, illustrated schematically in Figure. 1.3, ensures that the castor bean ribosomes are not inactivated by the toxic A chain. Because the proricin is segregated into the ER lumen as it is synthesized, a membrane barrier always exists between proricin or mature ricin and the ribosomes. The overall scheme for synthesis, transport and processing has now been established for a variety of plant protein body components, including lectins [144-147] and storage proteins [148, 149],... 

A preproricin gene from Ricinus communis has been characterized by both cDNA [31] and genomic [150] cloning. Southern blot analysis has indicated that the Ricinus communis genome includes at least six lectin genes [150], In our laboratory we constructed a cDNA library using ripening castor bean endosperm poly(A)+ RNA which had been enriched for lectin precursor... 

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