Ribosome-Templated Azide-Alkyne Cycloadditions: Synthesis of Potent Macrolide Antibiotics by In Situ Click Chemistry.

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TitleRibosome-Templated Azide-Alkyne Cycloadditions: Synthesis of Potent Macrolide Antibiotics by In Situ Click Chemistry.
Publication TypeJournal Article
Year of Publication2016
AuthorsGlassford, I, Teijaro, CN, Daher, SS, Weil, A, Small, MC, Redhu, SK, Colussi, DJ, Jacobson, MA, Childers, WE, Buttaro, B, Nicholson, AW, Mackerell, AD, Cooperman, BS, Andrade, RB
JournalJ Am Chem Soc
Volume138
Issue9
Pagination3136-44
Date Published2016 Mar 09
ISSN1520-5126
KeywordsAlkynes, Anti-Bacterial Agents, Azides, Click Chemistry, Cycloaddition Reaction, Humans, Macrolides, Models, Molecular, Ribosomes, Thermodynamics, Triazoles
Abstract

Over half of all antibiotics target the bacterial ribosome-nature's complex, 2.5 MDa nanomachine responsible for decoding mRNA and synthesizing proteins. Macrolide antibiotics, exemplified by erythromycin, bind the 50S subunit with nM affinity and inhibit protein synthesis by blocking the passage of nascent oligopeptides. Solithromycin (1), a third-generation semisynthetic macrolide discovered by combinatorial copper-catalyzed click chemistry, was synthesized in situ by incubating either E. coli 70S ribosomes or 50S subunits with macrolide-functionalized azide 2 and 3-ethynylaniline (3) precursors. The ribosome-templated in situ click method was expanded from a binary reaction (i.e., one azide and one alkyne) to a six-component reaction (i.e., azide 2 and five alkynes) and ultimately to a 16-component reaction (i.e., azide 2 and 15 alkynes). The extent of triazole formation correlated with ribosome affinity for the anti (1,4)-regioisomers as revealed by measured Kd values. Computational analysis using the site-identification by ligand competitive saturation (SILCS) approach indicated that the relative affinity of the ligands was associated with the alteration of macrolactone+desosamine-ribosome interactions caused by the different alkynes. Protein synthesis inhibition experiments confirmed the mechanism of action. Evaluation of the minimal inhibitory concentrations (MIC) quantified the potency of the in situ click products and demonstrated the efficacy of this method in the triaging and prioritization of potent antibiotics that target the bacterial ribosome. Cell viability assays in human fibroblasts confirmed 2 and four analogues with therapeutic indices for bactericidal activity over in vitro mammalian cytotoxicity as essentially identical to solithromycin (1).

DOI10.1021/jacs.5b13008
Alternate JournalJ. Am. Chem. Soc.
PubMed ID26878192
PubMed Central IDPMC4785600
Grant ListR01 GM070855 / GM / NIGMS NIH HHS / United States
GM051501 / GM / NIGMS NIH HHS / United States
R01 GM080376 / GM / NIGMS NIH HHS / United States
GM070855 / GM / NIGMS NIH HHS / United States
R01 AI080968 / AI / NIAID NIH HHS / United States
R01 GM051501 / GM / NIGMS NIH HHS / United States
R29 GM051501 / GM / NIGMS NIH HHS / United States
AI080968 / AI / NIAID NIH HHS / United States