Discovery of platencin, a dual FabF and FabH inhibitor with in vivo antibiotic properties

Abstract

Emergence of bacterial resistance is a major issue for all classes of antibiotics; therefore, the identification of new classes is critically needed. Recently we reported the discovery of platensimycin by screening natural product extracts using a target-based whole-cell strategy with antisense silencing technology in concert with cell free biochemical validations. Continued screening efforts led to the discovery of platencin, a novel natural product that is chemically and biologically related but different from platensimycin. Platencin exhibits a broad-spectrum Gram-positive antibacterial activity through inhibition of fatty acid biosynthesis. It does not exhibit cross-resistance to key antibiotic resistant strains tested, including methicillin-resistant Staphylococcus aureus, vancomycin-intermediate S. aureus, and vancomycin-resistant Enterococci. Platencin shows potent in vivo efficacy without any observed toxicity. It targets two essential proteins, ␤-ketoacyl-[acyl carrier protein (ACP)] synthase II (FabF) and III (FabH) with IC 50 values of 1.95 and 3.91 g/ml, respectively, whereas platensimycin targets only FabF (IC 50 ‫؍‬ 0.13 g/ml) in S. aureus, emphasizing the fact that more antibiotics with novel structures and new modes of action can be discovered by using this antisense differential sensitivity wholecell screening paradigm.platensimycin ͉ natural product ͉ thiolactomycin ͉ antisense ͉ fatty acid synthesis

Isolation, structure and biological activities of platensimycin B4 from Streptomyces platensis

“…The column was eluted with a step gradient of 40-100% aqueous methanol with 10% increments of MeOH. Two 600 ml fractions were collected from each 10% MeOH increments affording 14 fractions (Amberchrome fractions [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Amberchrome fractions 10-12 eluting with 80-90% MeOH were pooled and concentrated under reduced pressure, to remove most of the MeOH, to a volume of 200 ml mostly containing water.…”

“…[1][2][3][4] Discovery of these compounds was possible due to the design and introduction of a novel antisense differential sensitivity screening strategy in which FabH/FabF was sensitized. [3][4][5][6] Platensimycin is a selective inhibitor of the FabF acyl-enzyme intermediate and platencin is a balanced dual inhibitor of both FabH and FabF. Both of these compounds showed potent in vitro activities in both cell-free and whole-cell assay systems.…”

Coelomycin, a highly substituted 2,6-dioxo-pyrazine fungal metabolite antibacterial agent discovered by Staphylococcus aureus fitness test profiling

“…28 Hydrogenation of compound 1 with Pd/C afforded tetrahydro deoxy compound 4 (C 18 H 18 N 2 O 3 ) and tetrahydro dideoxy compound 5 (C 18 H 18 N 2 O 2 ). 13 C NMR spectrum (Table 2) (Table 2) due to loss of the N-oxy group. On the basis of the structure of 4 and 5, benzoyl group was placed at C-3 and structure 1 was assigned to compound 1.…”

“…No internal calibration was required; the instrument was calibrated once a week and checked daily to assure accuracy. All NMR spectra were recorded using a Varian Unity 500 ( 1 H, 500 MHz, 13 C, 125 MHz) spectrometer (Varian, Palo Alto, CA, USA). The residual proton of CD 2 Cl 2 was used as an internal reference (d H 5.32, d C 54.0).…”

“…4 The combination of these two approaches resulted in the discovery of a large number of natural products using either an rpsD-sensitized antisense strain [5][6][7][8][9][10] or fabH/fabF antisense-sensitized strains, including discovery of the FabF inhibitors platensimycin and platencin. [11][12][13][14][15][16][17] Recently, we have extended the antisense-based screening approach by constructing a S. aureus genome-wide fitness test assay and validated its use by mechanistically profiling a diverse set of 59 antibacterial compounds 18 and by the discovery of a new class of cell wall inhibitors. 19 Included in the S. aureus fitness test assay are 245 inducible antisense RNA strains engineered for reduced expression of genes essential for cell growth.…”