Capillary electrophoresis (CE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) have been employed as highly efficient methods to characterize ricin, its subunits, and the chemically deglycosylated forms. As a CE method, sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) was used because of its merit over the conventional slab gel techn...

Ricin, a member of the A-B family of ribosome-inactivating proteins, is classified as a Select Toxin by the Centers for Disease Control and Prevention because of its potential use as a biothreat agent. In an effort to engineer therapeutics for ricin, we recently produced a collection of alpaca-derived, heavy-chain only antibody VH domains (VHH or "nanobody") specific for ricin's enzymatic (RTA)...

Ricin, a highly toxic plant-derived toxin, is considered a potential weapon in biological warfare due to its 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. Passive immunization with polyclonal anti-ricin antibodies conferred protection against pulmonary ricinosis...

Due to widespread availability, toxicity, and potential for use as a bioterrorism agent, ricin is classified as a category B select agent. While ricin can be internalized by a number of routes, inhalation is particularly problematic. The resulting damage leads to irreversible pulmonary edema and death. Our study describes a model system developed to investigate the effects of ricin on respirato...

A hybrid molecule was constructed by covalently linking, by a disulfide bridge, the hormone insulin to the binding subunit B of the plant toxin ricin (specificity: Gal, GalNAc). Monolayer-cultured MDCK cells, which lack detectable levels of specific plasma membrane 125I-insulin binding but which readily bind 125I-insulin-ricin B, were used in these studies. Binding of insulin-ricin B to these c...

Upon intravenous injection into rats, the plant toxin ricin was rapidly cleared from the circulation by the liver. Among the different liver cell populations, most of the injected ricin associated with the sinusoidal endothelial cells (EC), whereas the liver parenchymal cells (PC) and Kupffer cells (KC) yielded minor contributions to the total liver uptake in vivo. Co-injection of mannan strong...

After endocytic uptake by mammalian cells, the cytotoxic protein ricin is transported to the endoplasmic reticulum, whereupon the A-chain must cross the lumenal membrane to reach its ribosomal substrates. It is assumed that membrane traversal is preceded by unfolding of ricin A-chain, followed by refolding in the cytosol to generate the native, biologically active toxin. Here we describe bioche...

Ribosome-inactivating proteins (RIPs) and sesquiterpenoid trichothecene mycotoxins are known to bind to eukaryotic ribosomes, inhibit translation and activate mitogen-activated protein kinases. Here we compared the capacities of the RIP ricin to promote 28S ribosomal RNA (rRNA) cleavage with that of the trichothecenes, deoxynivalenol (DON), and T-2 toxin (T-2). In a cell-free model, exposure to...

We used atomic force microscopy (AFM) and surface plasmon resonance (SPR) to study the surface conformations of an anti-ricin aptamer and its specific binding affinity for ricin molecules. The effect of surface modification of the Au(111) substrate on the aptamer affinity was also estimated. The AFM topography images had a resolution high enough to distinguish different aptamer conformations. T...

The B chain of ricin was expressed and delivered to the endoplasmic reticulum of tobacco protoplasts where it disappeared with time in a manner consistent with degradation. This turnover did not occur in the vacuoles or upon secretion. Indeed, several lines of evidence indicate that, in contrast to the turnover of endoplasmic reticulum-targeted ricin A chain in the cytosol, the bulk of expresse...