The Novel Aminomethylcycline Omadacycline Has High Specificity for the Primary Tetracycline-Binding Site on the Bacterial Ribosome.

Corina Heidrich,Christian Berens,Sanya Mitova,Sean Connell,Andreas Schedlbauer,Paola Fucini,Judith Steenbergen

doi:10.3390/antibiotics5040032

Abstract

Omadacycline is an aminomethylcycline antibiotic with potent activity against many Gram-positive and Gram-negative pathogens, including strains carrying the major efflux and ribosome protection resistance determinants. This makes it a promising candidate for therapy of severe infectious diseases. Omadacycline inhibits bacterial protein biosynthesis and competes with tetracycline for binding to the ribosome. Its interactions with the 70S ribosome were, therefore, analyzed in great detail and compared with tigecycline and tetracycline. All three antibiotics are inhibited by mutations in the 16S rRNA that mediate resistance to tetracycline in Brachyspira hyodysenteriae, Helicobacter pylori, Mycoplasma hominis, and Propionibacterium acnes. Chemical probing with dimethyl sulfate and Fenton cleavage with iron(II)-complexes of the tetracycline derivatives revealed that each antibiotic interacts in an idiosyncratic manner with the ribosome. X-ray crystallography had previously revealed one primary binding site for tetracycline on the ribosome and up to five secondary sites. All tetracyclines analyzed here interact with the primary site and tetracycline also with two secondary sites. In addition, each derivative displays a unique set of non-specific interactions with the 16S rRNA.

Highlights

Typical tetracyclines [1], like tetracycline (TET) or tigecycline (TGC), inhibit bacterial protein biosynthesis by binding to the 30S ribosomal subunit [2,3,4,5] and preventing stable accommodation of the EF-Tu-GTP-aa-tRNA complex at the ribosomal A-site [4,6]
Omadacycline Is Susceptible to 16S rRNA Mutations Conferring TET Resistance
It is known that OMC competes with TET for binding to the ribosome [13], it is unclear if this competition occurs at the primary and/or the many secondary tetracycline binding sites [3]

Summary

Introduction

Typical tetracyclines [1], like tetracycline (TET) or tigecycline (TGC), inhibit bacterial protein biosynthesis by binding to the 30S ribosomal subunit [2,3,4,5] and preventing stable accommodation of the EF-Tu-GTP-aa-tRNA complex at the ribosomal A-site [4,6]. Tetracyclines have broad-spectrum activity against many infectious disease agents, including Gram-negative and Gram-positive bacteria, intracellular pathogens, and even protozoan parasites (summarized in reference [7]). This, their low cost of production [8], and the absence of major adverse side-effects have led to their widespread application— for treating human and animal infections, and as prophylactic or growth-promoting agents in animal feed [9]. Antibiotics 2016, 5, 32; doi:10.3390/antibiotics5040032 www.mdpi.com/journal/antibiotics established tetracyclines. They have been grouped into two mechanisms, drug efflux and clinically established tetracyclines

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Conclusion