Sensitivity of Carrot Cell Cultures and RNA Polymerase II to Amatoxins : Evidence for the Inactivation of 6'-Hydroxyamatoxins |
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Authors: | Little M C Preston J F |
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Institution: | Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611. |
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Abstract: | Protoplast and cell suspension cultures of Daucus carota L. were evaluated for their sensitivity toward the three amatoxin derivatives, α-amanitin, 6′-deoxy-α-amanitin, and 6′-O-methyl-α-amanitin using inhibition of DNA synthesis to measure cell viability. Protoplasts appeared approximately 10-fold more refractory than suspension cells and α-amanitin was much less effective than the other two amatoxins, even though Ki values for isolated RNA polymerase II were similar (4-5 nanomolar). Additional studies evaluating the recoveries of all three amatoxins from cell suspension supernates indicate one basis for these differences to be the selective degradation of α-amanitin. A mechanism involving the activation of the hydroxyindole moiety of the α-amanitin is thus invoked to explain these differences and we postulate the involvement of plant oxidases in this role. |
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