Structures redefine the mechanism of action for tetracyclines

The tetracycline class of antibiotics is widely used for treating bacterial diseases including Lyme disease, anthrax, acne vulgaris, and pneumonia. Using a series of high-resolution cryo-electron microscopy (cryo-EM) structures, we show that tetracyclines can simultaneously target the mRNA decoding center and the nascent peptide exit tunnel (NPET) of the bacterial 70S ribosome. Among the tested tetracyclines, Doxycycline was unique in its ability to dimerize and bind the NPET at multiple locations. Structural comparison of Doxycycline, Minocycline, and Sarecycline bound to the Escherichia coli and Cutibacterium acnes 70S ribosome revealed species-specific differences affecting drug interaction and occupancy. Our results redefine the mechanism of action for tetracyclines and provide a structural basis for rational design of narrow spectrum tetracyclines to overcome the rising threat of antibiotic resistance.