New insights into the structural and functional involvement of the gate loop in AcrB export activity

Article


Ababou, A. 2017. New insights into the structural and functional involvement of the gate loop in AcrB export activity. Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics. 1866 (2), pp. 242-253.
AuthorsAbabou, A.
Abstract

AcrB is a major multidrug exporter in Escherichia coli and other Gram-negative bacteria. Its gate loop, located between the proximal and the distal pockets, have been reported to play important role in the export of many antibiotics. This loop location, rigidity and interactions with substrates have led recent reports to suggest that AcrB export mechanism operates in a sequential manner. First the substrate binds the proximal pocket in the access monomer, then it moves to bind the distal pocket in the binding monomer and subsequently it is extruded in the extrusion monomer. Recently, we have demonstrated that the gate loop is not required for the binding of Erythromycin but the integrity of this loop is important for an efficient export of this substrate. However, here we show that the antibiotic susceptibilities of the same AcrB gate loop mutants for Doxorubicin were unaffected, suggesting that this loop is not required for its export, and we demonstrate that this substrate may use principally the tunnel-1, located between transmembranes 8 and 9, more often than previously reported. To further explain our findings, here we address the gate loop mutations effects on AcrB solution energetics (fold, stability, molecular dynamics) and on the in vivo efflux of Erythromycin and Doxorubicin. Finally, we discuss the efflux and the discrepancy between the structural and the functional experiments for Erythromycin in these gate loop mutants.

KeywordsBacterial multidrug resistance; AcrB export mechanism; Drug susceptibility assay; X-ray crystallography; MD simulation
JournalBiochimica et Biophysica Acta (BBA) - Proteins and Proteomics
Journal citation1866 (2), pp. 242-253
ISSN1570-9639
Year2017
PublisherElsevier
Accepted author manuscript
License
Digital Object Identifier (DOI)doi:10.1016/j.bbapap.2017.11.003
Web address (URL)https://doi.org/10.1016/j.bbapap.2017.11.003
Publication dates
Online08 Nov 2017
Publication process dates
Deposited05 Dec 2017
Accepted05 Nov 2017
Accepted05 Nov 2017
Copyright information© 2017 Elsevier
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