Jul 10, 1976

Rates of different steps involved in the inhibition of protein synthesis by the toxic lectins abrin and ricin

The Journal of Biological Chemistry
S OlsnesA Pihl


The kinetics of protein synthesis inhibition in a cell-free system from rabbit reticulocyte lysate was studied after addition of abrin and ricin and the isolated A chains. The toxin A chains inhibited protein synthesis at a rate proportional to the amount added. When intact toxins were added to the reticulocyte lysate, the kinetics of protein synthesis inhibition indicated that the A chains must be liberated before ribosome inactivation can take place. The splitting of the toxin in the lysate was directly demonstrated by the use of labeled toxins. The amount of abrin and ricin bound to HeLa cells under different experimental conditions was correlated to the concomitant inhibition of cellular protein synthesis. In the presence of lactose, which inhibits toxin binding, much higher concentrations of toxins were required to inhibit protein synthesis than in the absence of lactose. A linear relationship was found between the lactose concentration in the medium and the toxin concentration required to give 50% reduction in protein synthesis after 3 hours. The amount of toxin bound to the cell surfaces in the presence of lactose was either determined directly or calculated from the apparent association constant between toxins and surfa...Continue Reading

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Mentioned in this Paper

Anhydrous lactose
RRNA N-glycosidase Activity
Abrin C
Protein Biosynthesis
Plasma Protein Binding Capacity
Metabolic Inhibition

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