456 research outputs found
Die Rolle des Internets in politischen Willensbildungsprozessen: Ergebnisse einer empirischen Analyse des Internets anlässlich der vorgezogenen Bundestagswahl 2005
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Adapting Yeast as Model to Study Ricin Toxin A Uptake and Trafficking
The plant A/B toxin ricin represents a heterodimeric glycoprotein belonging to the
family of ribosome inactivating proteins, RIPs. Its toxicity towards eukaryotic cells results
from the depurination of 28S rRNA due to the N-glycosidic activity of ricin toxin A chain,
RTA. Since the extention of RTA by a mammalian-specific endoplasmic reticulum (ER)
retention signal (KDEL) significantly increases RTA in vivo toxicity against mammalian
cells, we here analyzed the phenotypic effect of RTA carrying the yeast-specific ER
retention motif HDEL. Interestingly, such a toxin (RTAHDEL) showed a similar cytotoxic
effect on yeast as a corresponding RTAKDEL variant on HeLa cells. Furthermore, we
established a powerful yeast bioassay for RTA in vivo uptake and trafficking which is
based on the measurement of dissolved oxygen in toxin-treated spheroplast cultures of
S. cerevisiae. We show that yeast spheroplasts are highly sensitive against external applied
RTA and further demonstrate that its toxicity is greatly enhanced by replacing the
C-terminal KDEL motif by HDEL. Based on the RTA resistant phenotype seen in yeast
knock-out mutants defective in early steps of endocytosis (∆end3) and/or in RTA
depurination activity on 28S rRNA (∆rpl12B) we feel that the yeast-based bioassay
described in this study is a powerful tool to dissect intracellular A/B toxin transport from
the plasma membrane through the endosomal compartment to the ER
Correction: Becker, B. et al. Yeast Killer Toxin K28: Biology and Unique Strategy of Host Cell Intoxication and Killing
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