Citores L, Muñoz R, Rojo M A, Jiménez P, Ferreras J M, Girbés T
Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain.
Cell Mol Biol (Noisy-le-grand). 2003;49 Online Pub:OL461-5.
Nigrin b and ricin are type 2 (two chain) ribosome-inactivating proteins that exhibited nearly the same strong inhibitory activity on cell-free protein synthesis. Incubation of HeLa cells for 6 hr with ricin at 37 degrees C promoted protein synthesis inhibition with an IC50 of 0.2 ng/ml. Incubation of the cells for 6 hr at 18 degrees C abolished completely the inhibition. Incubation of HeLa cells with nigrin b for 6 hr at 37 degrees C was nearly 10(5) times less inhibitory than ricin. In contrast to the effects observed with ricin, incubation of HeLa cells with nigrin b at 18 degrees C slightly increased the inhibitory action on protein synthesis as compared with incubation at 37 degrees C. These results strongly support the hypothesis that the internalization of ricin and nigrin b could involve different receptors and therefore they could follow different intracellular pathways.
黑曲霉毒素b和蓖麻毒素是2型（双链）核糖体失活蛋白，它们对无细胞蛋白质合成表现出几乎相同的强烈抑制活性。在37℃下用蓖麻毒素处理HeLa细胞6小时，可促进蛋白质合成抑制，IC50为0.2 ng/ml。在18℃下将细胞孵育6小时可完全消除这种抑制作用。在37℃下用黑曲霉毒素b处理HeLa细胞6小时，其抑制作用比蓖麻毒素小近10^5倍。与用蓖麻毒素观察到的效果相反，在18℃下用黑曲霉毒素b处理HeLa细胞，与在37℃下孵育相比，对蛋白质合成的抑制作用略有增加。这些结果有力地支持了以下假设：蓖麻毒素和黑曲霉毒素b的内化可能涉及不同的受体，因此它们可能遵循不同的细胞内途径。
