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Updated: Sep 5, 2026

Nanomechanics of Drug-target Interactions and Antibacterial Resistance Detection
Published on: October 25, 2013
Structural basis for the antibiotic activity of ketolides and azalides
Frank Schlünzen1, Jörg M Harms, Francois Franceschi
1Max-Planck-Research Unit for Ribosomal Structure, 22603, Hamburg, Germany.
Abstract:
The azalide azithromycin and the ketolide ABT-773, which were derived by chemical modifications of erythromycin, exhibit elevated activity against a number of penicillin- and macrolide-resistant pathogenic bacteria. Analysis of the crystal structures of the large ribosomal subunit from Deinococcus radiodurans complexed with azithromycin or ABT-773 indicates that, despite differences in the number and nature of their contacts with the ribosome, both compounds exert their antimicrobial activity by blocking the protein exit tunnel. In contrast to all macrolides studied so far, two molecules of azithromycin bind simultaneously to the tunnel. The additional molecule also interacts with two proteins, L4 and L22, implicated in macrolide resistance. These studies illuminated and rationalized the enhanced activity of the drugs against specific macrolide-resistant bacteria.
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