Isolation, Structure, and Absolute Stereochemistry of Platensimycin, A Broad Spectrum Antibiotic Discovered Using an Antisense Differential Sensitivity Strategy

Abstract

Fatty acids are essential for survival of bacteria and are synthesized by a series of enzymes including the elongation enzymes, beta-ketoacyl acyl carrier protein synthase I/II (FabF/B). Inhibition of fatty acid synthesis is one of the new targets for the discovery and development of antibacterial agents. Platensimycin (1a) is a novel broad spectrum Gram-positive antibiotic produced by Streptomyces platensis. It was discovered by target-based whole-cell screening strategy using antisense differential sensitivity assay. It inhibits bacterial growth by selectively inhibiting condensing enzyme FabF of the fatty acid synthesis pathway and was isolated by a two-step process, a capture step followed by reversed-phase HPLC. The structure was elucidated by 2D NMR methods and confirmed by X-ray crystallographic analysis of a bromo derivative. It was determined that potential reactivity of the enone moiety does not play a key role in the biological activity of platensimycin. However, cyclohexenone ring conformation renders for the stronger binding interaction with the enzyme. The isolation, structure elucidation, derivatization, and biological activity of 6,7-dihydroplatensimycin are described.

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.…”

“…The basic solution was extracted three times with methylene chloride (3Â 450 ml). The methylene chloride extract was dried over anhydrous Na 2 No. …”

“…The discovery of platensimycin (1) and platencin (2) (Figure 1) from various strains of Streptomyces platensis generated significant excitement within the antibiotic research community. [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.…”

“…[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.…”

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

“…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.…”