Targeting the energy-coupling factor (ECF) transporters: identification of new tool compounds

Abstract

The energy-coupling factor (ECF) transporters are a family of transmembrane proteins involved in the uptake of vitamins in a wide range of bacteria. Inhibition of the activity of these proteins could reduce the viability of pathogens that depend on vitamin uptake. Their central role in the metabolism of bacteria and absence in humans make the ECF transporters a potential antibacterial target, which can be further investigated making use of a selective chemical probe. Here, we report on the virtual screening, design, synthesis, structure–activity relationships (SARs) and coarse-grained molecular dynamics simulations of the first class of inhibitors of the ECF transporters. We investigated the mechanism of action of this chemical class and profiled the best hit compounds regarding their pharmaceutical properties. The optimized hit has a minimum inhibitory concentration (MIC) value of 2 µg/mL against Streptococcus pneumoniae, which opens up the possibility to use this chemical class to investigate the role of the ECF transporters in health and disease.

An efficient way to screen inhibitors of energy-coupling factor (ECF) transporters in bacteria uptake assay

“…In our previous study, we showed that bacterial cells can be used efficiently to biologically evaluate compounds as potential inhibitors of an ECF transporter. 8 Specifically, an Escherichia coli strain that expresses heterologous ECF FolT2 from L. delbrueckii was used demonstrate on target activity. In the present study, we selected a Gram-positive strain (L. casei) due to its ability to import several essential vitamins such as folic acid, riboflavin, thiamine and biotin from the environment.…”

“…casei. 8 We reasoned that the difference in activity may be ascribed either to permeability issues of the compound or to a difference in the amino acid sequence of the ECF transporter between L.…”

“…Following our first publication, in which we used an in vitro transport-activity assay on purified ECF FolT2 reconstituted in proteoliposomes to identify hits 1 and 2 (Figure 2) 8 , we here present the establishment of a convenient functional, whole cell-based transport assay using L. casei in 96-well plates. The new whole-cell uptake assay was used to further validate and develop hit 2 into a more potent compound through a structure-activity relationship (SAR) study improving its properties and antibacterial activity.…”

Bacteriomimetic Liposomes Improve Antibiotic Activity of a Novel Energy-Coupling Factor Transporter Inhibitor

“…Sufficient bioavailability [9] is indispensable for efficient and safe antibiotic therapy, as the requirement for high antibiotic dosage, resulting from poor solubility, enhances the resistance formation of pathogens [10] and commensals [11]. In this work, we prepared a liposomal formulation of a novel compound related to previously reported inhibitors of ECF-transporters [12], HIPS5031 (Figure 1d, comprehensive information on the synthesis and characterization of HIPS5031 is given in the SI). Liposomes are a well-recognized strategy for improving the solubility of lipophilic compounds, which is of increasing significance since the majority of newly developed drugs are considered to be poorly soluble [13].…”

Structure-Guided Optimization of Small-Molecule Folate Uptake Inhibitors Targeting the Energy-Coupling Factor Transporters

“…We have recently reported a druggability assessment of the ECF-FolT as a novel and attractive antimicrobial target 12 alongside with a set of inhibitors as first tool compounds to explore the ECF transporters from a medicinal chemistry perspective. 13 Since previous studies were limited to tool compounds, we herein present the discovery of another chemical class that inhibits the folate uptake mediated by the ECF-FolT transporter and its further biological evaluation. By combining structure-based virtual screening of our in-house small molecule library and further examination of selected molecules via a Lactobacilius casei whole-cell assay our endeavors revealed in a highly promising hit compound bearing an ureidothiophene carboxylate core motif.…”