Interactions within the tripartite drug-efflux pumps of gram-negative bacteria

Marshall, Robert (2018). Interactions within the tripartite drug-efflux pumps of gram-negative bacteria. University of Birmingham. Ph.D.

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Antibiotic resistance, particularly amongst Gram-negative bacteria, has emerged as a major global concern. Working synergistically with the permeability barrier created by the cell envelope, multidrug efflux pumps contribute significantly to the intrinsic resistance of Gramnegative bacteria. Site-directed mutagenesis, informed by computational analyses, has been used on the prototypical tripartite efflux system, AcrAB-ToiC from Escherichia coli. Likely AcrA-ToiC interactions and functional roles of their sub-domains have been assessed using mutants in a combination of in vivo and in vitro approaches.

Results indicate that both the tip region and the equatorial domain, halfway up the ToiC channel, are involved in determining the compatibility of AcrA with ToiC. On the other side of the interaction, both the tip region and the helices of the AcrA hairpin are essential for normal function. The hairpin tip is required to maintain the permeability barrier, while the helices are necessary for a stable AcrA-ToiC interaction.

Combining these results with available literature, the first dynamic model of tripartite complex assembly is presented here. This model postulates initial bundling of AcrA and ToiC coiled-coil domains to open the ToiC channel followed by transition to a tip-to-tip interaction to drive channel closing and complex disassembly in an energy-dependent manner.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
College/Faculty: Colleges (2008 onwards) > College of Life & Environmental Sciences
School or Department: School of Biosciences
Funders: Other
Other Funders: Federation of European Microbiological Societies
Subjects: Q Science > QR Microbiology


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