Precursors of ricin and Ricinus communis agglutinin
- 1 January 1985
- journal article
- research article
- Published by Wiley in European Journal of Biochemistry
- Vol. 146 (2), 411-416
- https://doi.org/10.1111/j.1432-1033.1985.tb08667.x
Abstract
During synthesis in vivo the castor bean lectin precursors initially appear in the endoplasmic reticulum as a group of core glycosylated polypeptides of relative MW 64,000-68,000. Pretreatment of intact castor bean endosperm tissue with tunicamycin partially inhibits the cotranslational core glycosylation step and results in the accumulation of a single sized unglycosylated precursor polypeptide of relative molecular mass 59,000. The glycosylated precursors in the endoplasmic reticulum were enzymically converted to the 59,000-MW form by incubation with endoglucosaminidase H. Intracellular transport of the glycosylated lectin precursors from the endoplasmic reticulum to a denser vesicle fraction was accompanied by modifications to the oligosaccharide moieties which conferred resistance to the action of endoglucosaminidase H. The post-translational addition of fucose to the carbohydrate chain was identified as one of the oligosaccharide modification steps. Fucose addition was catalyzed by a glycosyltransferase associated with a smooth-surfaced membrane fraction which was distinct from the endoplasmic reticulum and which was tentatively identified as the Golgi apparatus. Glycosylation was not essential for intracellular transport of the lectin precursors: unglycosylated precursor synthesized in the presence of tunicamycin gave rise to unglycosylated lectin subunits in the protein bodies.This publication has 21 references indexed in Scilit:
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