Structural basis for translation inhibition by the glycosylated antimicrobial peptide Drosocin fromDrosophila melanogaster

Abstract

The proline-rich antimicrobial peptide (PrAMP) drosocin is produced by Drosophila species to combat bacterial infection. Unlike many PrAMPs, drosocin is O-glycosylated at threonine 11, a post-translation modification that enhances its antimicrobial activity. Here we demonstrate that the O-glycosylation influences not only cellular uptake of the peptide, but also interacts with its intracellular target, the ribosome. Cryo-electron microscopy structures of glycosylated drosocin on the ribosome at 2.1-2.8 A resolution reveal that the peptide interferes with translation termination by binding within the polypeptide exit tunnel and trapping RF1 on the ribosome, reminiscent of that reported for the PrAMP apidaecin. The glycosylation of drosocin enables multiple interactions with U2609 of the 23S rRNA, leading to conformational changes that break the canonical base-pair with A752. Collectively, our study provides novel molecular insights into the interaction of O-glycosylated drosocin with the ribosome, which provides a structural basis for future development of this class of antimicrobials.

Inhibition of translation termination by Drosocin, an antimicrobial peptide from fruit flies

“…Functionally important amino acid residues are not confined to the C-terminal portion of Dro sequence, but rather distributed through the entire length of the PrAMP and some of them (Lys2, Arg4, and Arg9) are found in the Dro's N-terminal segment. This finding is consistent with the cryo-EM structure of the ribosome-Dro complex (see the accompanying paper of Koller et al 57 ), where the entire peptide is well resolved due to the multiple interactions with the NPET. Our mutational data help to discern which of the contacts between Dro residues and the ribosome observed in the cryo-EM reconstructions of Koller at al.…”

“…Our mutational data help to discern which of the contacts between Dro residues and the ribosome observed in the cryo-EM reconstructions of Koller at al. 57 are essential for the PrAMP’s activity and which may play only a secondary role ( Extended Data Fig. 5 ).…”