biostudies-literatureGumbart JCNIAID NIH HHSMedical Research CouncilNational Institutes of Health3973-3982https://www.ebi.ac.uk/biostudies/studies/S-EPMC8510974biostudies-literatureUnknown120(18)The multidrug efflux pumps of Gram-negative bacteria are a class of complexes that span the periplasm, coupling both the inner and outer membranes to expel toxic molecules. The best-characterized example of these tripartite pumps is the AcrAB-TolC complex of Escherichia coli. However, how the complex interacts with the peptidoglycan (PG) cell wall, which is anchored to the outer membrane (OM) by Braun's lipoprotein (Lpp), is still largely unknown. In this work, we present molecular dynamics simulations of a complete, atomistic model of the AcrAB-TolC complex with the inner membrane, OM, and PG layers all present. We find that the PG localizes to the junction of AcrA and TolC, in agreement with recent cryo-tomography data. Free-energy calculations reveal that the positioning of PG is determBiophysical journalLpp positions peptidoglycan at the AcrA-TolC interface in the AcrAB-TolC multidrug efflux pump.PMC8510974MR/V000799/1MR/P019374/1R01 AI052293Gumbart JCHazel AJParks JMBeeby MZgurskaya HIFerreira JLHwang HCooper CJSmith JCfalseLpp positions peptidoglycan at the AcrA-TolC interface in the AcrAB-TolC multidrug efflux pump.The multidrug efflux pumps of Gram-negative bacteria are a class of complexes that span the periplasm, coupling both the inner and outer membranes to expel toxic molecules. The best-characterized example of these tripartite pumps is the AcrAB-TolC complex of Escherichia coli. However, how the complex interacts with the peptidoglycan (PG) cell wall, which is anchored to the outer membrane (OM) by Braun's lipoprotein (Lpp), is still largely unknown. In this work, we present molecular dynamics simulations of a complete, atomistic model of the AcrAB-TolC complex with the inner membrane, OM, and PG layers all present. We find that the PG localizes to the junction of AcrA and TolC, in agreement with recent cryo-tomography data. Free-energy calculations reveal that the positioning of PG is determ2021-01-01T00:00:00Z2021 Sep2026-05-08T01:49:25.288Z2025-04-19T22:47:59.289ZS-EPMC85109743441157610.1016/j.bpj.2021.08.016