Inhibition of Ricin A-Chain (RTA) Catalytic Activity by a Viral Genome-Linked Protein (VPg)
| Autor: | Valentina R. Aitbakieva, Shaneen Singh, Rahimah Ahmad, Artem V. Domashevskiy |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
0301 basic medicine
Models Molecular Reticulocytes viruses Allosteric regulation Potyvirus Biophysics Ricin Biochemistry Article Analytical Chemistry Protein–protein interaction 03 medical and health sciences chemistry.chemical_compound Viral Proteins Reticulocyte RNA Ribosomal 28S medicine Turnip mosaic virus Animals Molecular Biology Sequence Deletion 030102 biochemistry & molecular biology biology Cell-Free System Ricinus biology.organism_classification In vitro 030104 developmental biology medicine.anatomical_structure chemistry Depurination Thermodynamics Rabbits Protein Binding |
| Zdroj: | Biochim Biophys Acta Proteins Proteom |
| Popis: | Ricin is a plant derived protein toxin produced by the castor bean plant (Ricinus communis). The Centers for Disease Control (CDC) classifies ricin as a Category B biological agent. Currently, there is neither an effective vaccine that can be used to protect against ricin exposure nor a therapeutic to reverse the effects once exposed. Here we quantitatively characterize interactions between catalytic ricin A-chain (RTA) and a viral genome-linked protein (VPg) from turnip mosaic virus (TuMV). VPg and its N-terminal truncated variant, VPg1–110, bind to RTA and abolish ricin's catalytic depurination of 28S rRNA in vitro and in a cell-free rabbit reticulocyte translational system. RTA and VPg bind in a 1 to 1 stoichiometric ratio, and their binding affinity increases ten-fold as temperature elevates (5 °C to 37 °C). RTA-VPg binary complex formation is enthalpically driven and favored by entropy, resulting in an overall favorable energy, ΔG = −136.8 kJ/mol. Molecular modeling supports our experimental observations and predicts a major contribution of electrostatic interactions, suggesting an allosteric mechanism of downregulation of RTA activity through conformational changes in RTA structure, and/or disruption of binding with the ribosomal stalk. Fluorescence anisotropy studies show that heat affects the rate constant and the activation energy for the RTA-VPg complex, Ea = −62.1 kJ/mol. The thermodynamic and kinetic findings presented here are an initial lead study with promising results and provides a rational approach for synthesis of therapeutic peptides that successfully eliminate toxicity of ricin, and other cytotoxic RIPs. |
| Databáze: | OpenAIRE |
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