A role for the periplasmic adaptor protein AcrA in vetting substrate access to the RND efflux transporter AcrB

Ilyas Alav, Vassiliy N Bavro, Jessica M A Blair

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Tripartite resistance-nodulation-division (RND) efflux pumps, such as AcrAB-TolC of Salmonella Typhimurium, contribute to antibiotic resistance and comprise an inner membrane RND-transporter, an outer membrane factor, and a periplasmic adaptor protein (PAP). The role of the PAP in the assembly and active transport process remains poorly understood. Here, we identify the functionally critical residues involved in PAP-RND-transporter binding between AcrA and AcrB and show that the corresponding RND-binding residues in the closely related PAP AcrE, are also important for its interaction with AcrB. We also report a residue in the membrane-proximal domain of AcrA, that when mutated, differentially affects the transport of substrates utilising different AcrB efflux channels, namely channels 1 and 2. This supports a potential role for the PAP in sensing the substrate-occupied state of the proximal binding pocket of the transporter and substrate vetting. Understanding the PAP's role in the assembly and function of tripartite RND pumps can guide novel ways to inhibit their function to combat antibiotic resistance.

Original languageEnglish
Article number4752
JournalScientific Reports
Issue number1
Publication statusPublished - 19 Mar 2022

Bibliographical note

Funding Information:
I.A. was funded by the Midlands Integrative Biosciences Training Partnership (MIBTP2) and grant BBSRC BB/M01116X/1 at the University of Birmingham. V.N.B. was supported by funding from BBSRC (grant BB/N002776/1). J.M.A.B. was funded by the BBSRC grant BB/M02623X/1 (David Phillips Fellowship to J.M.A.B).

Publisher Copyright:
© 2022, The Author(s).


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