Year-end Sale % OFF 
Abstract
Salmonella is an important genus of Gram-negative pathogens, treatment of which has become problematic due to increases in antimicrobial resistance. This is partly attributable to the overexpression of tripartite efflux pumps, particularly the constitutively expressed AcrAB-TolC. Despite its clinical importance, the structure of the Salmonella AcrB transporter remained unknown to-date, with much of our structural understanding coming from the Escherichia coli orthologue. Here, by taking advantage of the styrene maleic acid (SMA) technology to isolate membrane proteins with closely associated lipids, we report the very first experimental structure of Salmonella AcrB transporter. Furthermore, this novel structure provides additional insight into mechanisms of drug efflux as it bears the mutation (G288D), originating from a clinical isolate of Salmonella Typhimurium presenting an increased resistance to fluoroquinolones. Experimental data are complemented by state-of-the-art molecular dynamics (MD) simulations on both the wild type and G288D variant of Salmonella AcrB. Together, these reveal several important differences with respect to the E. coli protein, providing insights into the role of the G288D mutation in increasing drug efflux and extending our understanding of the mechanisms underlying antibiotic resistance.
Highlights
Bacterial multidrug resistance (MDR) is a growing global concern with many antibiotics ineffective against major classes of pathogens
STmAcrBG288D structure was determined by single particle cryogenic electron microscopy (cryo-EM) to a global resolution of 4.6 Å
For protein extraction a styrene maleic acid (SMA) co-polymer approach was used, which we have previously shown to be effective at isolating the E. coli AcrB in sufficient levels for both negative-stain and cryo-EM analysis [36,37,39]
Summary
Bacterial multidrug resistance (MDR) is a growing global concern with many antibiotics ineffective against major classes of pathogens. This is especially pertinent in Gram-negative organisms, which are intrinsically more resistant due to the presence of a double membrane. The action of the resistance-nodulation-division (RND) transporter AcrB provides the principal antimicrobial resistance efflux function in Salmonella enterica serovar Typhimurium Typhimurium [5], seven form tripartite complexes with TolC [10], and AcrB is the primary transporter associated with MDR. Consistent with its major role, the loss of AcrB confers a loss of virulence in Salmonella [11] despite the considerable overlap of specificities and partial compensation from overexpression of homologous RND-based tripartite-pumps [12]. The presence of the AcrAB-TolC efflux pump is required for the development of ciprofloxacin resistance [13] and is essential for biofilm formation [14]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
