Modification, inhibition and function of elongation factor EF-P

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The fundamental process of protein synthesis is catalyzed on ribosomes. We have recently demonstrated that bacterial ribosomes become arrested when translating proteins contain consecutive polyproline stretches, and that this arrest is alleviated by the translation elongation factor EF-P. Furthermore, we could show that the post-translational ß-lysinylation of lysine34 of Escherichia coli EF-P by the enzymes YjeA and YjeK and the rhamnosylation of arginine32 of Shewanella EF-P by EarP, respectively, are critical for the rescue activity of EF-P. Many virulence factors contain polyproline stretches, explaining why modified EF-P is critical for bacterial pathogenicity. While EF-P is conserved, the modification enzymes YjeA and YjeK or EarP are absent in many bacterial phyla, even though these bacteria encode a high number of polyproline-containing proteins, thus suggesting the existence of novel EF-P modification pathways. Here we propose to identify and characterize these novel modification pathways, with a particular focus on phyla containing clinically important pathogenic bacteria, such as Firmicutes (e.g., Staphylococcus and Enterococcus) and Actinobacteria (e.g., Mycobacterium). In addition, we propose to apply an in vivo screening assay to identify low molecular weight EF-P inhibitors for the development of novel antimicrobial agents. Lastly, we aim to resolve structures of modified EF-P bound to polyproline-stalled ribosomes in order to elucidate the mechanism by which polyproline stretches stall ribosomes as well as how EF-P alleviates the translational arrest. Collectively, we believe our proposal will not only provide new functional and mechanistic insights into the fundamental process of translation, but also extend the spectrum of post-translational modification systems in general.