Abrin, ricin

Eiklid, K., Olsnes, S., and Pihl, A. (1980) Entry of lethal doses of abrin, ricin, and modeccin into the cytosol of Hela cells. Exp. Cell Res. 126, 321-326. 

Olsnes, S. (1978) Binding, entry, and action of abrin, ricin, and modeccin. In Transport of Macromolecules in Cellular Systems (S.C. Silverstein, ed.), pp. 103-116. Dahlem Konferenzen, Berlin. 

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... 

Abrin, ricin Inhibits binding of aminoacyl tRNA... 

Abrin, ricin, and their associated agglutinins (Olsnes and Pihl, 1977)... 

Olsnes, S. and Pihl, A. (1977) Abrin, ricin, and their associated agglutinins, in Cuatrecasas, P. (Ed.) The Specificity and Action of Animal, Bacterial, and Plant Toxins, London, New York, NY, Chapman and Hall. 

Phytohaemagglutinins.—Abrin, ricin, and their isolated A and B chains have been subjected to various chemical treatments and the effect of these on the biological activity of the lectins assessed. Reductive methylation, periodate oxidation, or succinylation of abrin or ricin reduced the toxicity and haemagglutinating ability of the former but not the latter. Treatment with A-acetylimidazole or A-bromosuccinimide resulted in strongly reduced toxicity of abrin and ricin, while 2-hydroxy-5-nitrobenzyl bromide had much less effect. 

K Sandvig, S Olsnes. (1982). Entry of toxic proteins abrin, modeccin, ricin, and diphtheria toxin into cells. I. Requirement for Ca2+. J Biol Chem 257 7495-7503. 

Due to the extraordinary toxicity of intact ribosome-inactivating toxins like ricin, abrin, and modeccin, purification and handling of these proteins must be done with extreme care. Even dust from crude seed powders or lyophilized proteins should be considered dangerous. During... 

Toxin A chains are isolated from ricin and abrin by reductive cleavage of the toxin, followed by separation of the chains These procedures are hazardous and should not be undertaken without the proper safeguards (4). 

Commercially obtained preparations of ricin A chain and abrin A chain may require further purification to eliminate traces of contaminating toxin B chains. The simplest procedure is to pass the A chain preparation over a column of Sepharose-linked asialofetuin, to which the B chains bind avidly (4,11)... 

Antibody-toxin conjugates made with ricin A chain, abrin A chain, gelomn, and momordin can be stored for at least 4 yr at -70°C without detectable loss of activity. The bond between the antibody and the RIP breaks down very slowly at 4°C in PBSE but, provided that care is taken to ensure the sterility of the solution, conjugates can be stored under these conditions for up to one year with little deterioration in quality. 

Knowles, P. P. and Thorpe, P. E. (1987) Purification of immunotoxins containing ricin A chain and abrin A chain using Blue Sepharose CL-6B. Anal Biochem. 160,440-443. 

This toxic protein is contained in caster seeds but does not pass into the oil. Similar phytotoxins occur in croton seeds (Crotin) jequirity seeds (Abrin) the bark of the locust tree, Robinia pseudo-acacia (Robin) and in the seeds of some leguminous plants (Phasin). The last is but weakly toxic. Ricin is responsible for the toxic effects on eating castor seeds 5 or 6 of these are fatal to a child, 20 to adults, and 3 or 4 seeds may cause violent gastroenteritis with nausea, headache, persistent vomiting, colic, sometimes bloody diarrhea, thirst, emaciation, and great debility. The symptoms usually do not set in until after several days. More severe intoxications cause small frequent pulse, cold sweat, icterus, and convulsions. Death occurs in 6 to 8 d, from the convulsions or from exhaustion. The fatality rate is about 6%. This low fatality rate is due to the destruction of the poison in the alimentary canal. The treatment would be evacuant and symptomatic. Usually, 3 to 10 d are required to complete recovery. 

Abrin, from jequirity beans (Abrus precatorius), resembles ricin so closely in its action that the difference was established only when it was noted that immunity against one did not constitute immunity against the other. 

The primary clinical targets of immunotoxins are tumors, based on the principle that the MAb will target the toxin to the tumor cells and the highly toxic moiety will then kill the cancer cells. Examples of toxins are ricin, diphtheria toxin and abrin, which are all glycoproteins. Their toxicity is based on their ability to block protein synthesis at the ribosomal protein assembly site. They are normally extremely toxic and not suitable for therapeutic purposes because they induce liver and vascular toxicity, even at low dose levels. 

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