RESUMEN
Screening large molecule libraries against pathogenic bacteria is often challenged by a low hit rate due to limited uptake, underrepresentation of antibiotic structural motifs, and assays that do not resemble the infection conditions. To address these limitations, we present a screen of a focused library of alkyl guanidinium compounds, a structural motif associated with antibiotic activity and enhanced uptake, under host-mimicking infection conditions against a panel of disease-associated bacteria. Several hit molecules were identified with activities against Gram-positive and Gram-negative bacteria, highlighting the fidelity of the general concept. We selected one compound (L15) for in-depth mode of action studies that exhibited bactericidal activity against methicillin-resistant Staphylococcus aureus USA300 with a minimum inhibitory concentration of 1.5 µM. Structure-activity relationship studies confirmed the necessity of the guanidinium motif for antibiotic activity. The mode of action was investigated using affinity-based protein profiling with an L15 probe and identified the signal peptidase IB (SpsB) as the most promising hit. Validation by activity assays, binding site identification, docking, and molecular dynamics simulations demonstrated SpsB activation by L15, a recently described mechanism leading to the dysregulation of protein secretion and cell death. Overall, this study highlights the need for unconventional screening strategies to identify novel antibiotics.
RESUMEN
Usnic acid is a natural product with versatile biological activities against various organisms. Here, we utilise a chemical proteomic strategy to gain insights into its target scope in bacterial and human cells. First, we excluded DNA binding as a major reason for its antibacterial activity, and second, we commenced with target profiling, which unravelled several metal cofactor-dependent enzymes in both species indicating a polypharmacological mode of action. Interestingly, our synthetic studies revealed a selectivity switch at usnic acid, which maintains antibacterial activity but lacks strong cytotoxic effects.
RESUMEN
PF74 is a capsid-targeting inhibitor of HIV replication that effectively perturbs the highly sensitive viral uncoating process. A lack of information regarding the optical purity (enantiomeric excess) of the single stereogenic centre of PF74 has resulted in ambiguity as to the potency of different samples of this compound. Herein is described the synthesis of enantiomerically enriched (S)- and (R)-PF74 and further enrichment of the samples (≥98%) using chiral HPLC resolution. The biological activities of each enantiomer were then evaluated, which determined (S)-PF74 (IC50 1.5 µM) to be significantly more active than (R)-PF74 (IC50 19 µM). Computational docking studies were then conducted to rationalise this large discrepancy in activity, which indicated different binding conformations for each enantiomer. The binding energy of the conformation adopted by the more active (S)-PF74 (ΔG = -73.8 kcal/mol) was calculated to be more favourable than the conformation adopted by the less active (R)-enantiomer (ΔG = -55.8 kcal/mol) in agreement with experimental observations.
Asunto(s)
Fármacos Anti-VIH/farmacología , Proteínas de la Cápside/metabolismo , Cápside/efectos de los fármacos , Infecciones por VIH/tratamiento farmacológico , VIH-1/efectos de los fármacos , Indoles/farmacología , Fenilalanina/análogos & derivados , Fármacos Anti-VIH/síntesis química , Fármacos Anti-VIH/química , Cápside/química , Cromatografía Líquida de Alta Presión , Células HEK293 , Humanos , Indoles/síntesis química , Indoles/química , Concentración 50 Inhibidora , Simulación del Acoplamiento Molecular , Fenilalanina/síntesis química , Fenilalanina/química , Fenilalanina/farmacología , EstereoisomerismoRESUMEN
Gigahertz- to terahertz-frequency infrared and Raman spectra contain a wealth of information concerning the structure, intermolecular forces, and dynamics of ionic liquids. However, these spectra generally have a large number of contributions ranging from slow diffusional modes to underdamped librations and intramolecular vibrational modes. This makes it difficult to isolate effects such as the role of Coulombic and hydrogen-bonding interactions. We have applied far-infrared and ultrafast optical Kerr effect spectroscopies on carefully selected ions with a greater or lesser degree of symmetry in order to isolate spectral signals of interest. This has allowed us to demonstrate the presence of longitudinal and transverse optical phonon modes and a great similarity of alkylammonium-based protic ionic liquids to liquid water. The data show that such phonon modes will be present in all ionic liquids, requiring a reinterpretation of their spectra.