SUMMARY
Antibiotic resistance ABC-Fs (ARE ABC-Fs) are translation factors currently proliferating among human pathogens that provide resistance against clinically important ribosome-targeting antibiotics. Here, we combine genetic and structural approaches to determine the regulation of streptococcal ARE ABC-F gene msrD in response to macrolide exposure and also demonstrate that MsrD twin-ATPase sites work asymmetrically to mediate the dynamic of MsrD interaction with the ribosome. We show that cladinose-containing macrolides lead to insertion of MsrDL leader peptide into an undocumented conserved crevice of the ribosomal exit tunnel concomitantly with 23S rRNA rearrangements that prevent peptide bond formation and preclude accommodation of release factors. The stalled ribosome obstructs formation of a Rho-independent terminator which prevents msrD transcriptional attenuation. This stalled ribosome is rescued by MsrD, but not by MsrD mutants which do not provide antibiotic resistance, showing evidence of equivalence between MsrD function in antibiotic resistance and its action on this complex.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
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Updated version of the manuscript. Title has been simplified. Abstract has been updated in view of new results. Main text has been modified in view of new results. Materials and methods have been updated accordingly. Figures 1C and 1D are new results. Previous Figures 1C to 1E are now in supplementary informations. Figure 2C has been modified by adding NusG pause motif. Figure 3D has been slightly modified by adding name and amino acid sequences of corresponding mutants. Current Figure 3E is a new result. Previous Figure 3E is now in supplementary informations. Figure 6B has been slightly modified to update general model. Supplementary Figure 4 has been corrected.