title: Interdomain flexibility and pH-induced conformational changes of AcrA revealed by molecular dynamics simulations.
abstract: The membrane fusion protein (MFP) AcrA is proposed to link the inner membrane transporter AcrB and outer membrane protein TolC, forming the tripartite AcrAB-TolC efflux pump, and was shown to be functionally indispensible. Structural and EPR studies showed that AcrA has high conformational flexibility and exhibited pH-induced conformational change. In this study, we built the complete structure of AcrA through homology modeling and performed atomistic simulations of AcrA at different pH values. It was shown that the conformational flexibility of AcrA originates from the motions of α-hairpin and MP domains. The conformational dynamics of AcrA is sensitive to specific point mutations and pH values. In agreement with the EPR experiments, the interdomain motions were restrained upon lowering pH from 7.0 to 5.0 in the simulations. It was found that the protonation/deprotonation of His285 underlies the pH-regulated conformational dynamics of AcrA by disturbing the local hydrogen bond interactions, suggesting that the changes of pH in the periplasm accompanying the drug efflux could act as a signal to trigger the action of AcrA, which undergoes reversible conformational rearrangement.
authors.affiliation: Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Shanghai, PR China.
authors.forename: Beibei
authors.initials: B
authors.lastname: Wang
authors.forename: Jingwei
authors.initials: J
authors.lastname: Weng
authors.forename: Kangnian
authors.initials: K
authors.lastname: Fan
authors.forename: Wenning
authors.initials: W
authors.lastname: Wang
mesh_terms: D016000:Cluster Analysis; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008074:Lipoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: C083497:AcrA protein, E coli; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D026901:Membrane Transport Proteins; D011994:Recombinant Proteins