Differential effects of nitrated ricin and nitrated and dithionite-reduced ricin on protein-synthesis inhibition and transmembrane tramsport in eukaryotic cells

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Abstract
Ricin1 was nitrated with tetranitromethane and reduced with sodium dithionite. Of the 8.0 nitro groups incorporated, 3.2 were on the A chain and 5.1 were on the B chain. Nitrated ricin1 was somewhat less active than nitrated and reduced ricin1 in inhibiting protein synthesis in vitro, but both were highly inhibitory. The modified toxins were less than 1% as active as ricin in inhibiting protein synthesis in cultured [mouse] cells. Indirect immunofluorescence assays demonstrated that both modified toxins were specifically bound to the cell surface and could be displaced by galactose.