Search Results (93)

Ricin and abrin are highly lethal Type II ribosome-inactivating proteins. They depurinate the same site of the 28S rRNA to inhibit protein synthesis. Consequently, standard molecular-level activity assays used to detect the toxic activity of ricin or abrin do not distinguish between the two in mixed samples without prior physical separation or specially designed substrates. This study proposes a novel, cost-effective method to separately and simultaneously quantify the activities of ricin and abrin in mixtures by exploiting their distinct thermal stabilities. Thermal inactivation was used to demonstrate that heating samples at 80 °C for 5 min maximized the difference in their activities; while ricin retained most of its activity, abrin activity dropped to 20% after thermal treatment. This thermal treatment yielded 4 standard curves—ricin or abrin, thermally treated or not treated—in the 0.3 to 50 µg/mL range. By applying Cramer’s rule, the individual concentrations of active ricin and abrin in mixed samples were successfully calculated. However, this method should be used with a method detecting presence of ricin/abrin, to avoid unexpected reactivity due to contaminating RIPs. Full article

Background/Objectives: Ribosome-inactivating proteins (RIPs) are plant-derived enzymes with potent cytotoxic activity, widely studied as anticancer agents, particularly as toxic payloads in immunoconjugates. Despite numerous encouraging results reported, their clinical application has been limited by their immunogenicity. RIPs from edible plants have been proposed as potentially more suitable candidates due to their possible improved tolerability. However, this aspect still requires validation in vivo in animal models. This study investigated the cytotoxic activity, mechanisms of action and translational potential of sodin 5 (a recently characterized type 1 RIP derived from the edible plant Salsola soda L.) in human colon cancer models, comparing it to the well-known type 1 RIP saporin-S6. Methods: The effects of sodin 5 and saporin-S6 on cell viability, cell death mechanisms and epithelial barrier integrity were assessed on HT29 and Caco-2 cell lines. Sodin 5 cross-reactivity with other anti-type 1 RIP sera was evaluated by ELISA. Finally, its structural characteristics were analyzed. Results: Sodin 5 showed a cytotoxic effect comparable to that of saporin-S6 in HT29 and Caco-2 colon cancer cells, with time- and concentration-dependent reductions in viability. Both type 1 RIPs disrupted the integrity of the intestinal epithelial barrier in mono- and co-culture models and predominantly activated the apoptotic pathway, without inducing necrosis. Sodin 5 exhibited limited immunological cross-reactivity and a conserved catalytic core, supporting its potential relevance as a therapeutic payload for intestinal cancer therapy. Conclusions: Our results indicate that sodin 5 possesses promising characteristics for anticancer applications, particularly in the treatment of intestinal malignancies, where local exposure and repeated administration are often required. Full article

Background/Objectives: Momordica charantia L. (Cucurbitaceae) (MC), commonly known as bitter melon, is a prominent therapeutic and edible species deeply rooted in traditional medicine for the management of diverse metabolic and infectious pathologies. Increasing evidence suggests that MC is a significant source of antiviral compounds that could act against many different types of viruses in humans. This narrative review summarizes the current knowledge regarding the antiviral properties of MC, with a focus on molecular mechanisms and therapeutic perspectives. Methods: A comprehensive literature search was conducted across the PubMed, Scopus and Web of Science databases, using the keywords “Momordica charantia”, “bitter melon”, “antiviral” and “MAP30”. Original in vitro, in vivo, in silico and mechanistic studies were included. Results: MC harbors diverse antiviral molecules acting through conserved and virus-specific mechanisms. Ribosome-inactivating proteins (RIPs) purified from MC display potent antiviral activity by catalyzing the depurination of viral RNA and DNA, inactivating host ribosomes and blocking protein synthesis. RIPs, especially MAP30, are among the most potent natural antiviral proteins described to date. Cucurbitane-type triterpenoids and other phytochemicals from MC also show antiviral activity. Conclusions: MC emerges as a promising candidate for the prevention/treatment of viral diseases through nutraceutical, topical and pharmaceutical applications. MC extracts could represent a resource to support the immune system and provide broad-spectrum benefits against viral infections or a tool for local treatments. Moreover, MC is a valuable source of various bioactive compounds that, after thorough pharmacological characterization, could be further developed into specific antiviral agents. Full article

Mirabilis antiviral protein (MAP) is the type I ribosome-inactivating protein (RIP), which consists of an RNA N-glycosylase domain with no carbohydrate-binding domain. Unlike many RIPs, such as ricin or trichosanthin, which inactivate eukaryotic ribosomes, MAP also inactivates the E. coli ribosome by cleaving the N-glycosidic bond at A2660 of 23S ribosomal RNA. The structure of the wild-type MAP has not been revealed yet. Here, we expressed, purified, and crystallized the plural recombinant MAPs, including both E168Q and R171Q mutations (MAP-EQRQ) in E. coli, and determined the crystal structure of MAP-EQRQ at 2.1 Å resolution. According to the predicted structure with RNA (sarcin-ricin loop) and the mutant protein’s activities using quantitative RT-PCR, we showed that residue R171 at the active site of MAP is a key residue to form the stable complex with target adenine. Furthermore, we showed that MAP bound the C-terminal domains of eukaryotic P2-stalk as well as E. coli L12-stalk. Full article

Plant-derived toxins such as ricin and abrin represent some of the most potent biological agents known, posing significant threats to public health and security due to their high toxicity, relative ease of extraction, and widespread availability. These ribosome-inactivating proteins (RIPs) have been implicated in politically and criminally motivated events, underscoring their critical importance in the context of biodefense. Public safety agencies, including law enforcement, customs, and emergency response units, require rapid, sensitive, and portable detection methods to effectively counteract these threats. However, many existing screening technologies lack the capability to detect biotoxins unless specifically designed for this purpose, revealing a critical gap in current biodefense preparedness. Consequently, there is an urgent need for robust, field-deployable detection platforms that operate reliably under real-world conditions. End-users in the security and public health sectors demand analytical tools that combine high specificity and sensitivity with operational ease and adaptability. This review provides a comprehensive overview of the biochemical characteristics of ricin and abrin, their documented misuse, and the challenges associated with their detection. Furthermore, it critically assesses key detection platforms—including immunoassays, mass spectrometry, biosensors, and lateral flow assays—focusing on their applicability in operational environments. Advancing detection capabilities within frontline services is imperative for effective prevention, timely intervention, and the strengthening of biosecurity measures. Full article

Sarcomas are very complex and clinically challenging mesenchymal tumors. Although the standard therapeutic approach has improved the 5-year survival rate, many patients experience local relapses and/or distant metastases. To improve patient outcome, new strategies need to be investigated. Immunotoxins (ITs) based on rRNA N-glycosylases (also named ribosome-inactivating proteins, RIPs) are promising tools for cancer therapy because, by combining rRNA-glycosylase’s high cytotoxicity with carrier selectivity, they can specifically eliminate target neoplastic cells. In the last few years, 3D models have been extensively used in cancer research, particularly for target-specific drug screening. This study aimed to evaluate the possibility of utilizing ribosome-inactivating protein (RIP)-containing ITs to selectively target TfR1-, EGFR1- and Her2-expressing sarcoma adherent cells (ACs), spheroids (SSs) and organoids (ORs). To compare Its’ efficacy and ability to induce apoptosis, we performed dose–response viability and caspase 3/7 activation assays on rhabdomyosarcoma and osteosarcoma ACs, SSs and ORs treated with Tf-IT, αEGFR1-IT and αHer2-IT. Our results indicate that, compared to the corresponding unconjugated RIPs, all ITs showed increased cytotoxicity in sarcoma ACs. Despite the increased complexity characterizing 3D models, the higher IC₅₀ differences between ITs and unconjugated RIPs were obtained in ORs, which appeared more resistant to the nonspecific killing of the RIPs than either the ACs or SSs, thus augmenting the therapeutic window between unconjugated and conjugated RIPs. IT induced a more delayed apoptosis in 3D compared to 2D models. Our results provide essential outcomes for the potential use of these RIP-based ITs as a therapeutic strategy to treat sarcoma. Full article

As a type II ribosome-inactivating protein (RIP-II) toxin, Ricin has garnered widespread recognition due to its inherent qualities as an easily prepared and highly stable substance, posing serious implications as a potential chemical and biological terrorist threat. For the detection of ricin, traditional immunoassay technologies, including methods like peptide cleavage combined with liquid chromatography mass spectrometry (LC-MS) or the more commonly used enzyme-linked immunosorbent assay (ELISA), have offered reliable results. However, these techniques are unfortunately limited by the requirement of a complex sample pretreatment process, which can be time-consuming and labor-intensive. In an effort to overcome these limitations, a highly sensitive and selective method was introduced via metal element labeling combined with inductively coupled plasma mass spectrometry (ICP-MS) in this research. The method centered on designing and synthesizing a europium-labeled compound (DOTA-NHS-Eu) that specifically targets the amino groups (-NH₂) on ricin. The compound, coupled with the application of specific magnetic beads, achieved the specific enrichment and subsequent quantitative detection of ricin by ICP-MS, which is based on the amount of europium element present. The established method demonstrated high specificity for ricin recognition, with a signal response to bovine serum protein that was found to be less than 10% of that for ricin. Furthermore, the calibration curve created for the method (y = 81.543x + 674.02 (R² > 0.99)) for quantifying ricin in a concentration range of 1.0–100 μg/mL demonstrated good linearity. The method was further evidenced by the limit of detection and quantitation results of 0.1 and 1.89 μg/mL, respectively. Collectively, these findings suggested that the research has offered a highly sensitive and selective method for ricin detection, which was not only easy to operate but also provided efficient results. The scheme showed great potential for the verification of chemical weapons and the destruction of toxic chemicals, therefore representing a significant advancement in the field of biomolecular detection and analysis. Full article

Malanin is a new type II ribosome-inactivating protein (RIP) purified from Malania oleifera, a rare, endangered tree is only found in the southwest of Guangxi Province and the southeast of Yunnan Province, China. The gene coding sequence of malanin was found from the cDNA library of M. oleifera seeds by employing the ten N-terminal amino acid sequences of malanin, DYPKLTFTTS for chain-A and DETXTDEEFN (X was commonly C) for chain-B. The results showed a 65% amino acid sequence homology between malanin and ricin by DNAMAN 9.0 software, the active sites of the two proteins were consistent, and the four disulfide bonds were in the same positions. The primary sequence and three-dimensional structures of malanin and ricin are likely to be very similar. Our studies suggest that the mechanism of action of malanin is expected to be analogous to ricin, indicating that it is a member of the type II ribosome-inactivating proteins. This result lays the foundation for further study of the anti-tumor activities of malanin, and for the application of malanin as a therapeutic agent against cancers. Full article

The family Caryophyllaceae comprises more than 2600 species spread widely across all the continents. Their economic importance is mainly as ornamentals (carnation) and as weeds in agriculture. Some species have been used traditionally (and some are still) in herbal medicine or as emulsifiers in food processing. These applications are based on the high content of triterpenoid saponins. Typical for this family are also ribosome-inactivating proteins (RIPs), which are potentially highly toxic. Agrostemma githago L. (common corncockle) was historically considered a serious toxicological hazard owing to cereal grain contamination by its seeds. Notwithstanding, it was also recommended as a drug by various herbalists. In this review, the literature was searched in the PubMed, Google Scholar, and Scopus databases for papers focused on the chemical composition and bioactivity of the two accepted species of the Agrostemma genus. This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and MetaAnalysis (PRISMA) guidelines. Current research reports the cytotoxicity against neoplastic cells; the protection against oxidative stress; the suppression of Leishmania major culture growth; the inhibition of protein synthesis; and the antiviral, anti-angiogenic, and antihypercholesterolemic activities of common corncockle. The future prospects of using A. githago saponins as adjuvants in drug formulations and enhancing the cytotoxicity of RIPs are also discussed. Full article

Saponin-mediated endosomal escape is a mechanism that increases the cytotoxicity of type I ribosome-inactivating proteins (type I RIPs). In order to actualize their cytotoxicity, type I RIPs must be released into the cytosol after endocytosis. Without release from the endosomes, type I RIPs are largely degraded and cannot exert their cytotoxic effects. Certain triterpene saponins are able to induce the endosomal escape of these type I RIPs, thus increasing their cytotoxicity. However, the molecular mechanism underlying the endosomal escape enhancement of type I RIPs by triterpene saponins has not been fully elucidated. In this report, we investigate the involvement of the basic amino acid residues of dianthin-30, a type I RIP isolated from the plant Dianthus caryophyllus L., in endosomal escape enhancement using alanine scanning. Therefore, we designed 19 alanine mutants of dianthin-30. Each mutant was combined with SO1861, a triterpene saponin isolated from the roots of Saponaria officinalis L., and subjected to a cytotoxicity screening in Neuro-2A cells. Cytotoxic screening revealed that dianthin-30 mutants with lysine substitutions did not impair the endosomal escape enhancement. There was one particular mutant dianthin, Arg24Ala, that exhibited significantly reduced synergistic cytotoxicity in three mammalian cell lines. However, this reduction was not based on an altered interaction with SO1861. It was, rather, due to the impaired endocytosis of dianthin Arg24Ala into the cells. Full article

The control of crop diseases caused by fungi remains a major problem and there is a need to find effective fungicides that are environmentally friendly. Plants are an excellent source for this purpose because they have developed defense mechanisms to cope with fungal infections. Among the plant proteins that play a role in defense are ribosome-inactivating proteins (RIPs), enzymes obtained mainly from angiosperms that, in addition to inactivating ribosomes, have been studied as antiviral, fungicidal, and insecticidal proteins. In this review, we summarize and discuss the potential use of RIPs (and other proteins with similar activity) as antifungal agents, with special emphasis on RIP/fungus specificity, possible mechanisms of antifungal action, and the use of RIP genes to obtain fungus-resistant transgenic plants. It also highlights the fact that these proteins also have antiviral and insecticidal activity, which makes them very versatile tools for crop protection. Full article

Ribosome-inactivating proteins (RIPs) are a group of proteins with rRNA N-glycosylase activity that irreversibly inhibit protein synthesis and consequently cause cell death. Recently, an RIP called ledodin has been found in shiitake; it is cytotoxic, strongly inhibits protein synthesis, and shows rRNA N-glycosylase activity. In this work, we isolated and characterized a 50 kDa cytotoxic protein from shiitake that we named edodin. Edodin inhibits protein synthesis in a mammalian cell-free system, but not in insect-, yeast-, and bacteria-derived systems. It exhibits rRNA N-glycosylase and DNA-nicking activities, which relate it to plant RIPs. It was also shown to be toxic to HeLa and COLO 320 cells. Its structure is not related to other RIPs found in plants, bacteria, or fungi, but, instead, it presents the characteristic structure of the fold type I of pyridoxal phosphate-dependent enzymes. Homologous sequences have been found in other fungi of the class Agaricomycetes; thus, edodin could be a new type of toxin present in many fungi, some of them edible, which makes them of great interest in health, both for their involvement in food safety and for their potential biomedical and biotechnological applications. Full article

The plant-derived toxin ricin is classified as a type 2 ribosome-inactivating protein (RIP) and currently lacks effective clinical antidotes. The toxicity of ricin is mainly due to its ricin toxin A chain (RTA), which has become an important target for drug development. Previous studies have identified two essential binding pockets in the active site of RTA, but most existing inhibitors only target one of these pockets. In this study, we used computer-aided virtual screening to identify a compound called RSMI-29, which potentially interacts with both active pockets of RTA. We found that RSMI-29 can directly bind to RTA and effectively attenuate protein synthesis inhibition and rRNA depurination induced by RTA or ricin, thereby inhibiting their cytotoxic effects on cells in vitro. Moreover, RSMI-29 significantly reduced ricin-mediated damage to the liver, spleen, intestine, and lungs in mice, demonstrating its detoxification effect against ricin in vivo. RSMI-29 also exhibited excellent drug-like properties, featuring a typical structural moiety of known sulfonamides and barbiturates. These findings suggest that RSMI-29 is a novel small-molecule inhibitor that specifically targets ricin toxin A chain, providing a potential therapeutic option for ricin intoxication. Full article

Ribosome inactivating proteins (RIPs) are specific N-β-glycosylases that are well-characterized in plants. Their enzymatic action is to damage ribosomes, thereby blocking protein translation. Recently, several research groups have been working on the screening for these toxins in edible plants to facilitate the use of RIPs as biotechnological tools and biopesticides and to overcome public prejudice. Here, four novel monomeric (type 1) RIPs have been isolated from the seeds of Atriplex hortensis L. var. rubra, which is commonly known as edible red mountain spinach. These enzymes, named hortensins 1, 2, 4, and 5, are able to release the β-fragment and, like many other RIPs, adenines from salmon sperm DNA, thus, acting as polynucleotide:adenosine glycosidases. Structurally, hortensins have a different molecular weight and are purified with different yields (hortensin 1, ~29.5 kDa, 0.28 mg per 100 g; hortensin 2, ~29 kDa, 0.29 mg per 100 g; hortensin 4, ~28.5 kDa, 0.71 mg per 100 g; and hortensin 5, ~30 kDa, 0.65 mg per 100 g); only hortensins 2 and 4 are glycosylated. Furthermore, the major isoforms (hortensins 4 and 5) are cytotoxic toward human continuous glioblastoma U87MG cell line. In addition, the morphological change in U87MG cells in the presence of these toxins is indicative of cell death triggered by the apoptotic pathway, as revealed by nuclear DNA fragmentation (TUNEL assay). Full article

Ribosome-inactivating proteins (RIPs) are plant toxins that were identified for their ability to irreversibly damage ribosomes, thereby causing arrest of protein synthesis and induction of cell death. The RIPs purified from Adenia plants are the most potent ones. Here, we describe a novel toxic lectin from Adenia heterophylla caudex, which has been named heterophyllin. Heterophyllin shows the enzymatic and lectin properties of type 2 RIPs. Interestingly, in immunoreactivity experiments, heterophyllin poorly cross-reacts with sera against all other tested RIPs. The cytotoxic effects and death pathways triggered by heterophyllin were investigated in three human-derived cell lines: NB100, T24, and MCF7, and compared to ricin, the most known and studied type 2 RIP. Heterophyllin was able to completely abolish cell viability at nM concentration. A strong induction of apoptosis, but not necrosis, and the involvement of oxidative stress and necroptosis were observed in all the tested cell lines. Therefore, the enzymatic, immunological, and biological activities of heterophyllin make it an interesting molecule, worthy of further in-depth analysis to verify its possible pharmacological application. Full article