RESUMEN
BACKGROUND: Cytochrome bd complexes are respiratory oxidases found exclusively in prokaryotes that are important during infection for numerous bacterial pathogens. METHODS: In silico docking was employed to screen approved drugs for their ability to bind to the quinol site of Escherichia coli cytochrome bd-I. Respiratory inhibition was assessed with oxygen electrodes using membranes isolated from E. coli and methicillin-resistant Staphylococcus aureus strains expressing single respiratory oxidases (ie, cytochromes bd, bo', or aa3). Growth/viability assays were used to measure bacteriostatic and bactericidal effects. RESULTS: The steroid drugs ethinylestradiol and quinestrol inhibited E. coli bd-I activity with median inhibitory concentration (IC50) values of 47 ± 28.9â µg/mL (158 ± 97.2â µM) and 0.2 ± 0.04â µg/mL (0.5 ± 0.1â µM), respectively. Quinestrol inhibited growth of an E. coli "bd-I only" strain with an IC50 of 0.06 ± 0.02â µg/mL (0.2 ± 0.07â µM). Growth of an S. aureus "bd only" strain was inhibited by quinestrol with an IC50 of 2.2 ± 0.43â µg/mL (6.0 ± 1.2â µM). Quinestrol exhibited potent bactericidal effects against S. aureus but not E. coli. CONCLUSIONS: Quinestrol inhibits cytochrome bd in E. coli and S. aureus membranes and inhibits the growth of both species, yet is only bactericidal toward S. aureus.
Asunto(s)
Antibacterianos , Escherichia coli , Staphylococcus aureus Resistente a Meticilina , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Escherichia coli/efectos de los fármacos , Escherichia coli/enzimología , Antibacterianos/farmacología , Simulación del Acoplamiento Molecular , Oxidorreductasas/antagonistas & inhibidores , Oxidorreductasas/metabolismo , Proteínas de Escherichia coli/antagonistas & inhibidores , Proteínas de Escherichia coli/metabolismo , Pruebas de Sensibilidad Microbiana , Esteroides/farmacología , Esteroides/química , Proteínas del Complejo de Cadena de Transporte de Electrón/antagonistas & inhibidores , Proteínas del Complejo de Cadena de Transporte de Electrón/metabolismo , Grupo Citocromo b , Citocromos/antagonistas & inhibidores , Citocromos/metabolismoRESUMEN
Antimicrobial peptides (AMPs) are compounds with a variety of bioactive properties. Especially promising are their antibacterial activities, often toward drug-resistant pathogens. Across different AMP sources, AMPs expressed within plants are relatively underexplored with a limited number of plant AMP families identified. Recently, we identified the novel AMPs CC-AMP1 and CC-AMP2 in ghost pepper plants (Capsicum chinense x frutescens), exerting promising antibacterial activity and not classifying into any known plant AMP family. Herein, AMPs related to CC-AMP1 and CC-AMP2 were identified within both Capsicum annuum and Capsicum baccatum. In silico predictions throughout plants were utilized to illustrate that CC-AMP1-like and CC-AMP2-like peptides belong to two broader AMP families, with three-dimensional structural predictions indicating that CC-AMP1-like peptides comprise a novel subfamily of α-hairpinins. The antibacterial activities of several closely related CC-AMP1-like peptides were compared with a truncated version of CC-AMP1 possessing significantly more activity than the full peptide. This truncated peptide was further characterized to possess broad-spectrum antibacterial activity against clinically relevant ESKAPE pathogens. These findings illustrate the value in continued study of plant AMPs toward characterization of novel AMP families, with CC-AMP1-like peptides possessing promising bioactivity.