We have used a protocol for internalization of ricin, a ligand binding to plasma membrane glycoproteins and glycolipids with terminal galactosyl residues, and infection with the vesicular stomatitis virus ts 045 mutant in BHK-21 cells to determine whether internalized plasma membrane molecules tagged by ricin reach distinct compartments of the biosynthetic-exocytic pathway. At 39.5 degrees C ne...

The kinetics of protein synthesis inhibition was studied in the choriocarcinoma-derived BeWo cell line treated with ricin and an immunotoxin (IT) constructed by linking a specific antibody to the A chain of ricin. The IT was specifically cytotoxic to BeWo and other choriocarcinoma cells. The multistep process underlying this kinetics was explored using two mathematical models where the protein ...

We have here studied the role of cholesterol in transport of ricin from endosomes to the Golgi apparatus. Ricin is endocytosed even when cells are depleted for cholesterol by using methyl-beta-cyclodextrin (m beta CD). However, as here shown, the intracellular transport of ricin from endosomes to the Golgi apparatus, measured by quantifying sulfation of a modified ricin molecule, is strongly in...

Ricin, a plant-derived exotoxin, inhibits protein synthesis by ribosomal inactivation. Due to its wide availability and ease of preparation, ricin is considered a biothreat, foremost by respiratory exposure. We examined the in vivo interactions between ricin and cells of the lungs in mice intranasally exposed to the toxin and revealed multi-phasic cell-type-dependent binding profiles. While mac...

The plant toxin ricin is transported retrogradely from the cell surface to the endoplasmic reticulum (ER) from where the enzymatically active part is retrotranslocated to the cytosol, presumably by the same mechanism as used by misfolded proteins. The ER degradation enhancing alpha-mannosidase I-like protein, EDEM, is responsible for directing aberrant proteins for ER-associated protein degrada...

With the use of the cytochemical stain for horseradish peroxidase of Graham and Karnovsky (1966. J. Histochem. Cytochem.14:291), conjugates of horseradish peroxidase with ricin, wheat germ agglutinin, and phytohemagglutinin were employed for the morphologic demonstration of d-galactose (ricin), N-acetylglucosamine (wheat germ), and N-acetylgalactosamine (phytohemagglutinin) containing moieties ...

Ricin is a protein toxin found only in mature castor (Ricinus communis L., Euphorbiaceae) seed that enzymatically destroys the ribosomes of eukaryotes. The presence of ricin in the high protein meal of castor has historically reduced its value as an animal feed. Since ricin has the potential to be used as a chemical warfare and bioterrorism agent, the production and processing of castor has und...

Ricin, a highly toxic plant-derived toxin, is considered a potential weapon in biowarfare and bioterrorism due to its pronounced toxicity, high availability, and ease of preparation. Pulmonary exposure to ricin results in the generation of an acute edematous inflammation followed by respiratory insufficiency and death. Massive neutrophil recruitment to the lungs may contribute significantly to ...

A toxic lectin, ricin D, present in the seeds of Ricinus communis has been purified and crystallized in a form suitable for high resolution crystallographic structure studies. This protein is different from a previously found form of ricin (also present in the same seeds), the only ricin for which a preliminary x-ray investigation has been reported so far. Ricin D crystallizes from an aqueous s...

Experiments have been made to test whether the toxic lectin ricin can be bound to and introduced into cells by some other mechanism than via its B chain, the natural binding moiety of the toxin, without its toxic effect being neutralized. Complexes consisting of ricin and antibodies specifically directed against ricin B chain were incubated with mouse peritoneal macrophages and rat Kupffer cell...