COVID-19: Mechanisms of the Antiviral Activities of Selective Antibiotics Targeting the Human 80S Ribosome

Background: The majority of scientists, physicians, and healthcare professionals were trained with the paradigm: “antibiotics are for bacteria only !”, because they misunderstood the definition of the ribosome targeting antibiotics. In the context of the current worldwide COVID-19 pandemic, it might be useful to recall as precisely as possible the definition of the word antibiotic and provide evidence that some classes of antibiotics could offer excellent means to counteract viral infections via specific mechanisms. Methods: Molecular modeling and docking studies were used, as well as the tRNAox labeling reaction of the ribosomal protein eL42 in situ on human 80S ribosomes to demonstrate that cycloheximide and its thiosemicarbazone analogues bind to the catalytic Lys-53 residue of the human large subunit ribosomal protein eL42. Results: Comparison of the binding sites for Cycloheximide (CHX) and Sparsomycin (SPS) on the evolutionarily conserved E. coli bL12 and S. cerevisiae eL42 by means of molecular modeling and docking studies showed that: (i) SPS binds in proximity to the catalytic Lys-65 residue of the GANK motif of rp bL12 and to the catalytic Lys-55 residue of the GGQTKP motif of rp eL42; (ii) CHX failed to bind to the GANK motif, while the glutarimide moiety of SPS and CHX was found to make contact with Lys-55 of the GGQTKP motif of rp eL42. Conclusion: In this report, we demonstrate that cycloheximide and its thiosemicarbazone analogues are capable of inhibiting the human 80S ribosomes selectively through their binding to the ε-amino group of the side chain of Lys-53. As a consequence, these small-molecule inhibitors of translation are susceptible to exhibit antiviral activities by preventing the human ribosomes of the SARS-CoV-2 infected cells from synthesizing the viral proteins and enzymes.