Bacterial chemoreceptors mediate chemotactic responses to diverse stimuli. Here, by using an integrated in silico, in vitro, and in vivo approach, we screened a large compound library and found eight novel chemoeffectors for the Escherichia coli chemoreceptor Tar. Six of the eight new Tar binding compounds induce attractant responses, and two of them function as antagonists that can bind Tar without inducing downstream signaling. Comparison between the antagonist and attractant binding patterns suggests that the key interactions for chemotaxis signaling are mediated by the hydrogen bonds formed between a donor group in the attractant and the main-chain carbonyls (Y149 and/or Q152) on the α4 helix of Tar. This molecular insight for signaling is verified by converting an antagonist to an attractant when introducing an N-H group into the antagonist to restore the hydrogen bond. Similar signal triggering effect by an O-H group is also confirmed. Our study suggests that the Tar chemoeffector binding pocket may be separated into two functional regions: region I mainly contributes to binding and region II contributes to both binding and signaling. This scenario of binding and signaling suggests that Tar may be rationally designed to respond to a nonnative ligand by altering key residues in region I to strengthen binding with the novel ligand while maintaining the key interactions in region II for signaling. Following this strategy, we have successfully redesigned Tar to respond to L-arginine, a basic amino acid that does not have chemotactic effect for WT Tar, by two site-specific mutations (R69′E and R73′E).T wo-component signaling pathways are ubiquitous in bacteria. They enable the cells to recognize and respond to different environmental stimuli (1). The control network of bacterial chemotaxis uses such a two-component system to sense the extracellular chemoeffector concentrations (2, 3). Chemoreceptors are the key upstream sensory components in the chemotaxis signaling pathway. They directly interact with specific extracellular chemoeffectors and transfer environmental information to the downstream response regulator, which ultimately controls the cell's motility (4, 5).Tar is one of the major chemoreceptors found in Escherichia coli and Salmonella enterica serovar Typhimurium (6). Attractant and repellent molecules that can induce chemotactic responses of the cells by interacting with Tar were studied (7). In addition to these two types of chemoeffectors, antagonist molecules that can directly bind to chemoreceptors without generating chemotactic responses should also exist. For example, antagonists for the sensor kinase TodS were found in the TodS/TodT two-component system (8). However, so far, antagonist molecules that function by directly binding to E. coli chemoreceptors have not been reported.Much progress has been made in understanding the structural basis of chemoreceptor signaling. Crystal structures show that each monomer (in the Tar homodimer) contains a four-helix bundle (helices α1-α4) structure, of w...
Persisters are a small fraction of drug-tolerant bacteria without any genotype variations. Their existence in many life-threatening infectious diseases presents a major challenge to antibiotic therapy. Persistence is highly related to toxin−antitoxin modules. HipA (high persistence A) was the first toxin found to contribute to Escherichia coli persistence. In this study, we used structure-based virtual screening for HipA inhibitors discovery and identified several novel inhibitors of HipA that remarkably reduced E. coli persistence. The most potent one decreased the persister fraction by more than five-fold with an in vitro K D of 270 ± 90 nM and an ex vivo EC 50 of 46 ± 2 and 28 ± 1 μM for ampicillin and kanamycin screening, respectively. These findings demonstrated that inhibition of toxin can reduce bacterial persistence independent of the antibiotics used and provided a framework for persistence treatment by interfering with the toxin−antitoxin modules.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.