Modes of action of tunicamycin, liposidomycin B, and mureidomycin A: inhibition of phospho-N-acetylmuramyl-pentapeptide translocase from Escherichia coli

Abstract

Using a continuous fluorescence-based enzyme assay, we have characterized the antibacterial agents tumicamycin and liposidomycin B as inhibitors of solubilized Escherichia coli phospho-N-acetylmuramyl-pentapeptide translocase. Tunicamycin exhibited reversible inhibition (Ki = 0.55 +/- 0.1 microM) which was noncompetitive with respect to the lipid acceptor substrate and competitive with respect to the fluorescent substrate analog, dansyl-UDPMurNAc-pentapeptide. Liposidomycin B exhibited slow-binding inhibition (Ki = 80 +/- 15 nM) which was competitive with respect to the lipid acceptor substrate and noncompetitive with respect to dansyl-UDPMurNAc-pentapeptide. These results provide insight into the molecular mechanisms of action of these two classes of nucleoside antibiotics.

Quinovosamycins: new tunicamycin-type antibiotics in which the α, β-1″,11′-linked N-acetylglucosamine residue is replaced by N-acetylquinovosamine

“…[7][8][9] The mode of action is known, with the TUN-Mg 2+ complex established as a transition state analog for several hexosamine-1-phosphate:prenol phosphate translocases. 10,11 A biosynthetic pathway has been proposed for TUN in which the 11-carbon dialdose sugar, tunicamine, is derived from uridine and N-acetylglucosamine. [12][13][14] The pseudoribosyl ring of tunicamine is N-glycosidically linked to uracil to form a structure highly analogous to the nucleoside uridine, and is presumed to mimic the UMP leaving group in the transition state for the translocase-catalyzed reactions.…”

Intrinsic resistance of Escherichia coli to mureidomycin A and C due to expression of the multidrug efflux system AcrAB-TolC: comparison with the efflux systems of mureidomycin-susceptible Pseudomonas aeruginosa

“…These agents act by inhibition of peptidoglycan synthesis due to inhibition of phospho-N-acetylmuramyl-pentapeptide-translocase. 2 However, Escherichia coli is extremely resistant to mureidomycins, even though peptidoglycan synthesis is inhibited in vitro by mureidomycin A to the same extent as it is in the mureidomycin-susceptible r-RNA group I bacterium P. aeruginosa. 3 Efflux systems traversing bacterial cell surfaces transport xenobiotics, including antimicrobial agents, from the cell interior to an external space, and function as a self-defense mechanism against such agents.…”

MraY Inhibitors as Novel Antibacterial Agents

“…These assays brought additional information mostly because they were enzymatic activity based assays and consequently permitted mechanistic studies. Generally, these assays were performed with UDP-MurNAc-pentapeptide that bore a fluorescence probe and the principle was based upon the difference of fluorescence observed between dansylated UDP-MurNAcpentapeptide and dansylated Lipid-I [19,20].…”