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Analytical Biochemistry Sep 2024Ricin is one of the most toxic substances known and a type B biothreat agent. Shiga toxins (Stxs) produced by E. coli (STEC) and Shigella dysenteriae are foodborne...
Ricin is one of the most toxic substances known and a type B biothreat agent. Shiga toxins (Stxs) produced by E. coli (STEC) and Shigella dysenteriae are foodborne pathogens. There is no effective therapy against ricin or STEC and there is an urgent need for inhibitors. Ricin toxin A subunit (RTA) and A1 subunit of Stx2a (Stx2A1) bind to the C-terminal domain (CTD) of the ribosomal P-stalk proteins to depurinate the sarcin/ricin loop. Modulation of toxin-ribosome interactions has not been explored as a strategy for inhibition. Therefore, development of assays that detect inhibitors targeting toxin-ribosome interactions remains a critical need. Here we describe a fluorescence anisotropy (FA)-based competitive binding assay using a BODIPY-TMR labeled 11-mer peptide (P11) derived from the P-stalk CTD to measure the binding affinity of peptides ranging from 3 to 11 amino acids for the P-stalk pocket of RTA and Stx2A1. Comparison of the affinity with the surface plasmon resonance (SPR) assay indicated that although the rank order was the same by both methods, the FA assay could differentiate better between peptides that show nonspecific interactions by SPR. The FA assay detects only interactions that compete with the labeled P11 and can validate inhibitor specificity and mechanism of action.
Topics: Ricin; Fluorescence Polarization; Ribosomes; Surface Plasmon Resonance; Shiga Toxin; Binding, Competitive; Protein Binding; Shiga Toxin 2
PubMed: 38825159
DOI: 10.1016/j.ab.2024.115580 -
AMB Express May 2024Ribosome-inactivating proteins (RIPs) are highly active N-glycosidases that depurinate both bacterial and eukaryotic rRNAs, halting protein synthesis during translation....
Ribosome-inactivating proteins (RIPs) are highly active N-glycosidases that depurinate both bacterial and eukaryotic rRNAs, halting protein synthesis during translation. Found in a diverse spectrum of plant species and tissues, RIPs possess antifungal, antibacterial, antiviral, and insecticidal properties linked to plant defense. In this study, we investigated the physiochemical properties of RIP peptides from the Cucurbitaceae family through bioinformatics approaches. Molecular weight, isoelectric point, aliphatic index, extinction coefficient, and secondary structures were analyzed, revealing their hydrophobic nature. The novelty of this work lies in the comprehensive examination of RIPs from the Cucurbitaceae family and their potential therapeutic applications. The study also elucidated the binding interactions of Cucurbitaceae RIPs with key biological targets, including Interleukin-6 (IL-6). Strong hydrogen bond interactions between RIPs and these targets suggest potential for innovative insilico drug design and therapeutic applications, particularly in cancer treatment. Comprehensive analysis of bond lengths using Ligpolt + software provides insights for optimizing molecular interactions, offering a valuable tool for drug design and structural biology studies.
PubMed: 38801471
DOI: 10.1186/s13568-024-01718-z -
Biomolecular NMR Assignments Jun 2024Ricin is a potent plant toxin that targets the eukaryotic ribosome by depurinating an adenine from the sarcin-ricin loop (SRL), a highly conserved stem-loop of the rRNA....
Ricin is a potent plant toxin that targets the eukaryotic ribosome by depurinating an adenine from the sarcin-ricin loop (SRL), a highly conserved stem-loop of the rRNA. As a category-B agent for bioterrorism it is a prime target for therapeutic intervention with antibodies and enzyme blocking inhibitors since no effective therapy exists for ricin. Ricin toxin A subunit (RTA) depurinates the SRL by binding to the P-stalk proteins at a remote site. Stimulation of the N-glycosidase activity of RTA by the P-stalk proteins has been studied extensively by biochemical methods and by X-ray crystallography. The current understanding of RTA's depurination mechanism relies exclusively on X-ray structures of the enzyme in the free state and complexed with transition state analogues. To date we have sparse evidence of conformational dynamics and allosteric regulation of RTA activity that can be exploited in the rational design of inhibitors. Thus, our primary goal here is to apply solution NMR techniques to probe the residue specific structural and dynamic coupling active in RTA as a prerequisite to understand the functional implications of an allosteric network. In this report we present de novo sequence specific amide and sidechain methyl chemical shift assignments of the 267 residue RTA in the free state and in complex with an 11-residue peptide (P11) representing the identical C-terminal sequence of the ribosomal P-stalk proteins. These assignments will facilitate future studies detailing the propagation of binding induced conformational changes in RTA complexed with inhibitors, antibodies, and biologically relevant targets.
Topics: Ricin; Nuclear Magnetic Resonance, Biomolecular; Nitrogen Isotopes; Protein Subunits; Amino Acid Sequence
PubMed: 38642265
DOI: 10.1007/s12104-024-10172-8 -
Molecules (Basel, Switzerland) Mar 2024The 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...
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.
Topics: Animals; Mice; Ricin; Ribosome Inactivating Proteins, Type 2; Drug Development; Hydrolases; Liver
PubMed: 38611715
DOI: 10.3390/molecules29071435 -
RNA Biology Jan 2024RNA modifications, including -7-methylguanosine (mG), are pivotal in governing RNA stability and gene expression regulation. The accurate detection of internal mG...
RNA modifications, including -7-methylguanosine (mG), are pivotal in governing RNA stability and gene expression regulation. The accurate detection of internal mG modifications is of paramount significance, given recent associations between altered mG deposition and elevated expression of the methyltransferase METTL1 in various human cancers. The development of robust mG detection techniques has posed a significant challenge in the field of epitranscriptomics. In this study, we introduce two methodologies for the global and accurate identification of mG modifications in human RNA. We introduce borohydride reduction sequencing (Bo-Seq), which provides base resolution mapping of mG modifications. Bo-Seq achieves exceptional performance through the optimization of RNA depurination and scission, involving the strategic use of high concentrations of NaBH, neutral pH and the addition of 7-methylguanosine monophosphate (mGMP) during the reducing reaction. Notably, compared to NaBH-based methods, Bo-Seq enhances the mG detection performance, and simplifies the detection process, eliminating the necessity for intricate chemical steps and reducing the protocol duration. In addition, we present an antibody-based approach, which enables the assessment of mG relative levels across RNA molecules and biological samples, however it should be used with caution due to limitations associated with variations in antibody quality between batches. In summary, our novel approaches address the pressing need for reliable and accessible methods to detect RNA mG methylation in human cells. These advancements hold the potential to catalyse future investigations in the critical field of epitranscriptomics, shedding light on the complex regulatory roles of mG in gene expression and its implications in cancer biology.
Topics: Humans; RNA; Nucleotides; Methylation; Methyltransferases; RNA Processing, Post-Transcriptional; Guanosine
PubMed: 38566310
DOI: 10.1080/15476286.2024.2337493 -
Bioorganic & Medicinal Chemistry Feb 2024Ricin, a category-B agent for bioterrorism, and Shiga toxins (Stxs), which cause food poisoning bind to the ribosomal P-stalk to depurinate the sarcin/ricin loop. No...
Ricin, a category-B agent for bioterrorism, and Shiga toxins (Stxs), which cause food poisoning bind to the ribosomal P-stalk to depurinate the sarcin/ricin loop. No effective therapy exists for ricin or Stx intoxication. Ribosome binding sites of the toxins have not been targeted by small molecules. We previously identified CC10501, which inhibits toxin activity by binding the P-stalk pocket of ricin toxin A subunit (RTA) remote from the catalytic site. Here, we developed a fluorescence polarization assay and identified a new class of compounds, which bind P-stalk pocket of RTA with higher affinity and inhibit catalytic activity with submicromolar potency. A lead compound, RU-NT-206, bound P-stalk pocket of RTA with similar affinity as a five-fold larger P-stalk peptide and protected cells against ricin and Stx2 holotoxins for the first time. These results validate the P-stalk binding site of RTA as a critical target for allosteric inhibition of the active site.
Topics: Binding Sites; Peptides; Protein Binding; Ribosomes; Ricin
PubMed: 38340640
DOI: 10.1016/j.bmc.2024.117614 -
IScience Sep 2023High-power screening (HPS) technologies, such as DNA-encoded library (DEL) technology, could exponentially increase the dimensions of the chemical space accessible for...
High-power screening (HPS) technologies, such as DNA-encoded library (DEL) technology, could exponentially increase the dimensions of the chemical space accessible for drug discovery. The intrinsic fragile nature of DNA is associated with cumbersome limitations and DNA durability (e.g., depurination, loss of phosphate groups, adduct formation) is compromised in numerous organic chemistry conditions that require empirical testing. An atlas of reaction conditions (temperature, pH, solvent/buffer, ligands, oxidizing reagents, catalysts, scavengers in function of time) that have been systematically tested in multiple combinations, indicates precisely limits useful for DEL construction. More importantly, this approach could be used broadly to effectively evaluate DNA-compatibility of any novel on-DNA chemical reaction, and it is compatible with different molecular methodologies. This atlas and the general approach presented, by allowing novel reaction conditions to be performed in presence of DNA, should greatly help in expanding the DEL chemical space as well as any field involving DNA durability.
PubMed: 37664608
DOI: 10.1016/j.isci.2023.107573 -
Nucleic Acids Research Oct 2023Xeno-nucleic acids (XNAs) have gained significant interest as synthetic genetic polymers for practical applications in biomedicine, but very little is known about their...
Xeno-nucleic acids (XNAs) have gained significant interest as synthetic genetic polymers for practical applications in biomedicine, but very little is known about their biophysical properties. Here, we compare the stability and mechanism of acid-mediated degradation of α-l-threose nucleic acid (TNA) to that of natural DNA and RNA. Under acidic conditions and elevated temperature (pH 3.3 at 90°C), TNA was found to be significantly more resistant to acid-mediated degradation than DNA and RNA. Mechanistic insights gained by reverse-phase HPLC and mass spectrometry indicate that the resilience of TNA toward low pH environments is due to a slower rate of depurination caused by induction of the 2'-phosphodiester linkage. Similar results observed for 2',5'-linked DNA and 2'-O-methoxy-RNA implicate the position of the phosphodiester group as a key factor in destabilizing the formation of the oxocarbenium intermediate responsible for depurination and strand cleavage of TNA. Biochemical analysis indicates that strand cleavage occurs by β-elimination of the 2'-phosphodiester linkage to produce an upstream cleavage product with a 2'-threose sugar and a downstream cleavage product with a 3' terminal phosphate. This work highlights the unique physicochemical properties available to evolvable non-natural genetic polymers currently in development for biomedical applications.
PubMed: 37650628
DOI: 10.1093/nar/gkad716 -
National Science Review Aug 2023Current DNA base editors contain nuclease and DNA deaminase that enables deamination of cytosine (C) or adenine (A), but no method for guanine (G) or thymine (T) editing...
Current DNA base editors contain nuclease and DNA deaminase that enables deamination of cytosine (C) or adenine (A), but no method for guanine (G) or thymine (T) editing is available at present. Here we developed a deaminase-free glycosylase-based guanine base editor (gGBE) with G editing ability, by fusing Cas9 nickase with engineered N-methylpurine DNA glycosylase protein (MPG). By several rounds of MPG mutagenesis via unbiased and rational screening using an intron-split EGFP reporter, we demonstrated that gGBE with engineered MPG could increase G editing efficiency by more than 1500 fold. Furthermore, this gGBE exhibited high base editing efficiency (up to 81.2%) and high G-to-T or G-to-C (i.e. G-to-Y) conversion ratio (up to 0.95) in both cultured human cells and mouse embryos. Thus, we have provided a proof-of-concept of a new base editing approach by endowing the engineered DNA glycosylase the capability to selectively excise a new type of substrate.
PubMed: 37404457
DOI: 10.1093/nsr/nwad143