Molecular interaction between ribosome-inactivating proteins and triterpene saponins

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Ribosome-inactivating proteins (RIPs) are toxins that irreversibly inactivate the cellular protein machinery thus triggering cell death. RIPs are produced by certain plants that do also produce particular low molecular glycosides, which are termed triterpensaponins. Both components are sequestered within the plants’ seeds. We have shown that triterpensaponins massively increase the toxicity of RIPs. This effect relies on the ability of the triterpensaponins to drag the RIPs through biological membranes resulting in an increase of the cytosolic RIP concentration. In further studies we could demonstrate that the dragger function of triterpensaponins may be utilized for antibody-RIP-conjugates and non-viral gene delivery thus demonstrating the tremendous potential as platform technology for drug-delivery in general.Interaction analysis have shown that triterpensaponins bind to RIPs and further biophysical investigations indicate the formation of nanoparticulate triterpensaponin-RIP-complexes leading to an enhanced membrane penetration of the RIPs. It is hypothesized that this is facilitated by the formation of triterpensaponin-micelles encapsulating RIPs. Triterpensaponins are known to form micelles and micelles are in turn known to penetrate through biological membranes. The aim of the current project is to investigate the molecular interaction of triterpensaponins and RIPs. For this purpose in silico methods will be performed in order to identify the binding sites of the triterpensaponins on the RIP. By mutational approaches the appropriate binding sites will be than stepwise changed to non-binding sites. By using cell- and biophysical based methods the significance of these binding sites for the dragging function and the complex formation will be investigated.The basic insights provided by the results of this project might be the starting point for the development of novel innovative strategies to increase the intracellular delivery of drugs.