Tetracenomycin X sequesters peptidyl-tRNA during translation of QK motifs

As antimicrobial resistance threatens our ability to treat common bacterial infections, new antibiotics with limited cross-resistance are urgently needed. In this regard, natural products that target the bacterial ribosome have the potential to be developed into potent drugs through structure-guided design, provided their mechanisms of action are well understood. Here we use inverse toeprinting coupled to next-generation sequencing to show that the aromatic polyketide tetracenomycin X primarily inhibits peptide bond formation between an incoming aminoacyl-tRNA and a terminal Gln-Lys (QK) motif in the nascent polypeptide. Using cryogenic electron microscopy, we reveal that translation inhibition at QK motifs occurs via an unusual mechanism involving sequestration of the 3 & PRIME; adenosine of peptidyl-tRNA(Lys) in the drug-occupied nascent polypeptide exit tunnel of the ribosome. Our study provides mechanistic insights into the mode of action of tetracenomycin X on the bacterial ribosome and suggests a path forward for the development of novel aromatic polyketide antibiotics.

Automated summary

As antimicrobial resistance becomes a threat, the development of new antibiotics with limited cross-resistance is urgent. Natural products that target the bacterial ribosome have the potential to be potent drugs if their mechanisms of action are well understood. This study provides mechanistic insights into how the aromatic polyketide tetracenomycin X inhibits peptide bond formation and suggests a path forward for the development of novel antibiotics.