Allosteric drug transport mechanism of multidrug transporter AcrB

• Published in: Nature communications Vol. 12; no. 1; p. 3889
• Main Authors: Tam, Heng-Keat, Foong, Wuen Ee, Oswald, Christine, Herrmann, Andrea, Zeng, Hui, Pos, Klaas M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29-06-2021; Nature Publishing Group; Nature Portfolio
• Subjects: 13; 38; 38/70; 631/326/22/1434; 631/326/41/2536; 631/45/173; 631/535/1266; 82/83; Allosteric properties; Antibiotic resistance; Antibiotics; Bacteria; Binding sites; Catalysis; Domains; Drugs; E coli; Efflux; Erythromycin; Function analysis; Fusidic acid; Gram-negative bacteria; Humanities and Social Sciences; Hydrogen; Linezolid; multidisciplinary; Novobiocin; Oxacillin; Pumps; Science; Science (multidisciplinary); Structure-function relationships; Substrates
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-24151-3

Gram-negative bacteria maintain an intrinsic resistance mechanism against entry of noxious compounds by utilizing highly efficient efflux pumps. The
E. coli
AcrAB-TolC drug efflux pump contains the inner membrane H
+
/drug antiporter AcrB comprising three functionally interdependent protomers, cycling consecutively through the loose (L), tight (T) and open (O) state during cooperative catalysis. Here, we present 13 X-ray structures of AcrB in intermediate states of the transport cycle. Structure-based mutational analysis combined with drug susceptibility assays indicate that drugs are guided through dedicated transport channels toward the drug binding pockets. A co-structure obtained in the combined presence of erythromycin, linezolid, oxacillin and fusidic acid shows binding of fusidic acid deeply inside the T protomer transmembrane domain. Thiol cross-link substrate protection assays indicate that this transmembrane domain-binding site can also accommodate oxacillin or novobiocin but not erythromycin or linezolid. AcrB-mediated drug transport is suggested to be allosterically modulated in presence of multiple drugs.
Gram-negative bacteria can display intrinsic antibiotic resistance due to the action of tripartite efflux pumps, which include a H
+
/drug antiporter component. Here, the authors present a structure-function analysis of antiporter AcrB in intermediate states of the transport cycle, showing novel drug-binding sites and transport pathways.