Inhibition of Staphyloxanthin Virulence Factor Biosynthesis in Staphylococcus aureus: In Vitro, in Vivo, and Crystallographic Results

Abstract

The gold color of Staphylococcus aureus is derived from the carotenoid staphyloxanthin, a virulence factor for the organism. Here, we report the synthesis and activity of a broad variety of staphyloxanthin biosynthesis inhibitors that inhibit the first committed step in its biosynthesis, condensation of two farnesyl diphosphate (FPP) molecules to dehydrosqualene, catalyzed by the enzyme dehydrosqualene synthase (CrtM). The most active compounds are phosphonoacetamides that have low nanomolar Ki values for CrtM inhibition and are active in whole bacterial cells and in mice, where they inhibit S. aureus disease progression. We also report the X-ray crystallographic structure of the most active compound, N-3-(3-phenoxyphenyl)propylphosphonoacetamide (IC50 = 8 nM, in cells), bound to CrtM. The structure exhibits a complex network of hydrogen bonds between the polar headgroup and the protein, while the 3-phenoxyphenyl side chain is located in a hydrophobic pocket previously reported to bind farnesyl thiodiphosphate (FsPP), as well as biphenyl phosphonosulfonate inhibitors. Given the good enzymatic, whole cell, and in vivo pharmacologic activities, these results should help guide the further development of novel antivirulence factor-based therapies for S. aureus infections.

Lipophilic analogs of zoledronate and risedronate inhibit Plasmodium geranylgeranyl diphosphate synthase (GGPPS) and exhibit potent antimalarial activity

“…In addition, we included phosphonosulfonates and related systems known to inhibit head-to-head prenyl synthases (22)(23)(24) such as dehydrosqualene synthase and squalene synthase (31), which could also inhibit Plasmodium phytoene synthase, and cationic species (such as Ro 48-8071 and quinuclidines), some of which are known to inhibit Plasmodium cell growth (28,32). The structures of all 560 compounds are shown in Fig.…”

“…These lipophilic bisphosphonates have far more potent activity both in vitro and in vivo than do conventional bisphosphonates in tumor cell-growth inhibition and γδ T-cell-activation assays (20, 21) as well as against malaria parasites (14). In this work, we elected to screen our in-house library of 560 prenyl-synthase inhibitors, developed over the past decade as anticancer drug leads and as antibacterials (20)(21)(22)(23)(24), for their activity in P. falciparum growth inhibition inside red cells. We discovered two potent leads, BPH-703 and BPH-811 (Scheme 1), lipophilic analogs of the commercial drugs zoledronate and risedronate, and determined their crystal structures bound to P. vivax…”

Synthesis and evaluation of 5′-modified thymidines and 5-hydroxymethyl-2′-deoxyuridines as Mycobacterium tuberculosis thymidylate kinase inhibitors

“…For this purpose two non-commercial Horner reagents were self-made (Scheme 1). Diethyl ((methylsulfonyl)methyl)phosphonate 6 was prepared according to known procedures [7], while Horner reagent 9 was obtained by reacting half an equivalent of chlorodiethylphosphate with bis-lithiated 8 [8,9]. 3'-Silylated thymidine 12 was produced by a selective cleavage of the primary TBDMS group on 11 [10,11].…”

Inhibition of staphyloxanthin biosynthesis in Staphylococcus aureus by rhodomyrtone, a novel antibiotic candidate

“…The first committed step in the staphyloxanthin biosynthetic pathway proceeds through presqualene diphosphate and then dehydrosqualene, catalysed by CrtM (Pelz et al, 2005), and is very similar to that catalysed by SQS in plants, animals and some protozoa, as demonstrated in Fig. 1 (Song et al, 2009b). Liu et al (2008) recently observed that the crystal structure of S. aureus CrtM is very similar to that of human SQS used in cholesterol biosynthesis in humans (Liu et al, 2008).…”

“…Staphyloxanthin has been associated with enhancing bacterial survival in harsh environments and during infections (Giachino et al, 2001; Kahlon et al, 2010). The membrane pigment promotes resistance to reactive oxygen species (ROS) such as O 2 2 , H 2 O 2 and HOCl generated by host neutrophils (Lang et al, 2000;Clauditz et al, 2006;Song et al, 2009b).…”