Interaction Study of Ribosome-inactivating Proteins (RIPs) and Ribosomes and Increasing the Specificity of Ricin A Chain toward HIV-1 Protease by Protein Engineering

Ribosome-inactivating proteins (RIPs) are N-glycosidases that inactivate ribosome by removing a specific adenine from the sarcin-ricin loop (SRL) of 23S or 28S ribosomal RNA. Ribosomal proteins are critical for determining the ribosome specificity of RIPs as they assist RIPs to get access to the SRL. Ribosome specificity and potency of RIPs are highly varied although their tertiary structures and catalytic depurination are highly alike. Moreover, it is still unsolved why only a few RIPs acquiring the ability to inhibit both prokaryotic and eukaryotic ribosomes. We attempted to elucidate the phenomena by investigating the interactions of maize RIP with eukaryotic ribosome and shiga toxin with prokaryotic ribosome.;Here we showed maize RIP presents a novel docking site to interact with ribosomal protein P2 and demonstrated the structure of RIPs imposes a large constraint on the nature and strength of the interaction with ribosomal protein which in turn affect the potency of RIPs on the ribosome. Shiga toxin was found to interact with prokaryotic ribosome weaker than the eukaryotic ribosome and crosslinked to the bacterial ribosomal protein L7/L10. Additionally, we increased the HIV-1 specificity of ricin A chain by incorporating the HIV-1 protease specific peptide to the C-terminus of the toxin and hope our findings would help to extend similar scheme to other RIPs in the future.