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A Methyl 4‑Oxo-4-phenylbut-2-enoate with in Vivo Activity against MRSA That Inhibits MenB in the Bacterial Menaquinone Biosynthesis Pathway

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journal contribution
posted on 07.03.2016, 00:00 authored by Joe S. Matarlo, Yang Lu, Fereidoon Daryaee, Taraneh Daryaee, Bela Ruzsicska, Stephen G. Walker, Peter J. Tonge
4-Oxo-4-phenyl-but-2-enoates inhibit MenB, the 1,4-dihydroxyl-2-naphthoyl-CoA synthase in the bacterial menaquinone (MK) biosynthesis pathway, through the formation of an adduct with coenzyme A (CoA). Here, we show that the corresponding methyl butenoates have minimum inhibitory concentration (MIC) values as low as 0.35–0.75 μg/mL against drug-sensitive and -resistant strains of Staphylococcus aureus. Mode of action studies on the most potent compound, methyl 4-(4-chlorophenyl)-4-oxobut-2-enoate (1), reveal that 1 is converted into the corresponding CoA adduct in S. aureus cells and that this adduct binds to the S. aureus MenB (saMenB) with a Kd value of 2 μM. The antibacterial spectrum of 1 is limited to bacteria that utilize MK for respiration, and the activity of 1 can be complemented with exogenous MK or menadione. Finally, treatment of methicillin-resistant S. aureus (MRSA) with 1 results in the small colony variant phenotype, and thus 1 phenocopies knockout of the menB gene. Taken together, the data indicate that the antibacterial activity of 1 results from a specific effect on MK biosynthesis. We also evaluated the in vivo efficacy of 1 using two mouse models of MRSA infection. Notably, compound 1 increased survival in a systemic infection model and resulted in a dose-dependent decrease in bacterial load in a thigh infection model, validating MenB as a target for the development of new anti-MRSA candidates.