92121-68-1Relevant articles and documents
Immunity-Guided Identification of Threonyl-tRNA Synthetase as the Molecular Target of Obafluorin, a β-Lactone Antibiotic
Alt, Silke,Batey, Sibyl F. D.,Chandra, Govind,Francklyn, Christopher S.,Scott, Thomas A.,Wiencek, Patrick,Wilkinson, Barrie
, (2019)
To meet the ever-growing demands of antibiotic discovery, new chemical matter and antibiotic targets are urgently needed. Many potent natural product antibiotics which were previously discarded can also provide lead molecules and drug targets. One such example is the structurally unique β-lactone obafluorin, produced by Pseudomonas fluorescens ATCC 39502. Obafluorin is active against both Gram-positive and -negative pathogens; however, the biological target was unknown. We now report that obafluorin targets threonyl-tRNA synthetase, and we identify a homologue, ObaO, which confers immunity to the obafluorin producer. Disruption of obaO in P. fluorescens ATCC 39502 results in obafluorin sensitivity, whereas expression in sensitive E. coli strains confers resistance. Enzyme assays demonstrate that E. coli threonyl-tRNA synthetase is fully inhibited by obafluorin, whereas ObaO is only partly susceptible, exhibiting a very unusual partial inhibition mechanism. Altogether, our data highlight the utility of an immunity-guided approach for the identification of an antibiotic target de novo and will ultimately enable the generation of improved obafluorin variants.
Synthesis, Stability, and Antimicrobial Activity of (+)-Obafluorin and Related β-Lactone Antibiotics
Pu, Yunlong,Lowe, Christopher,Sailer, Miloslav,Vederas, John C.
, p. 3642 - 3655 (2007/10/02)
Optically pure obafluorin (1), an antibacterial agent from Pseudomonas fluorescens, was synthesized in six steps via lactonization of N--(2S,3R)-2-amino-3-hydroxy-4-(4-nitrophenyl)butanoic acid (12a), which was prepared in a stereospecific manner from 4-nitrophenylacetaldehyde (9a) and (S)-1-benzoyl-2-tert-butyl-3-methyl-4-imidazolidinone (7).A series of analogues was then synthesized in order to probe structural features required for antibacterial activity as well as those responsible for the hydrolytic decomposition of 1 to the corresponding hydroxy acid 23a.Analogues 22b and 22c wherein the nitro group of 1 is replaced with hydrogen and chlorine, respectively, were prepared in a fashion similar to 1, as were the N-acetyl, N-benzoyl, and N-2-(2-aminothiazol-4-yl)-2-(methoxyimino)acetyl (ATMO) derivatives 24a-c.The tosylate salt of L-threonine-β-lactone (21) was transformed to a series of N-acylated derivatives including the following: 22d (2,3-dihydroxybenzoyl), 25 (2-hydroxybenzoyl), 27 (3,4-dihydroxybenzoyl), 29 (4'-methyl-2,2'-bipyridine-4-carbonyl), 31 (ε-(L-α-aminoadipoyl)), 34 ((N'-2,3-dihydroxybenzoyl)-β-alanyl), 35 (bromoacetyl), 36 ((6-purinylthio)acetyl), and 37 ((4-pyridylthio)acetyl).The results show that α-amino β-lactones bearing an N-acyl group with an o- or p-hydroxybenzoyl moiety are especially prone to decomposition under aqueous conditions and that this effect is enhanced by replecement of the 4-nitrobenzyl group on the oxetanone ring of 1 with a methyl.The N-(3,4-dihydroxybenzoyl)-L-threonine β-lactone (27) converts slowly in the solid state to (4S,5S)-2-(3,4-dihydroxybenzoyl)-5-methyl-2-oxazoline-4-carboxylic acid (39b), which hydrolyzes rapidly in 4:1 CD3CN:D2O to O-(3,4-dihydroxybenzoyl)-L-allothreonine (38b).Direct hydrolysis of 27 to 38b under the same conditions has a half-life of 2.4 days.Preliminary assays for antibacterial activity indicate that 29 has nearly comparable activity to obafluorin (1) but is much more stable.The (2-nitrophenyl)sulfenyl β-lactones 14 and 41, as well as the N-(phenylsulfenyl)-L-threonine β-lactone (44), are the most active agents in the biological assays.
