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Structural insights into a substrate translocation pathway revealed by the RND efflux pump complex MexJK from

Zhikun Wu1, Ziyue Meng2, Wei Huang3

  • 1Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China.

Science Advances
|August 7, 2026
PubMed

Insights

This study reveals a novel drug transport pathway in Pseudomonas aeruginosa

Area of Science:

  • Microbiology
  • Structural Biology
  • Biochemistry

Background:

  • Resistance-nodulation-cell division (RND) efflux pumps are a primary mechanism of multidrug resistance in Pseudomonas aeruginosa.
  • The inner membrane protein MexK forms a tripartite efflux complex with MexJ and outer membrane proteins to export drugs like triclosan.

Purpose of the Study:

  • To elucidate the molecular mechanism of triclosan transport by the MexJK efflux pump in Pseudomonas aeruginosa.
  • To determine the cryo-electron microscopy (cryo-EM) structures of apo-MexK and the triclosan-bound MexJK complex.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) to resolve structures.
  • Molecular dynamics simulations to analyze transport pathways.
  • Site-directed mutagenesis to identify key residues.

Main Results:

  • Determined high-resolution cryo-EM structures of apo-MexK and the MexJK-triclosan complex.
  • Identified a unique triclosan-binding pocket within the MexK transmembrane domain.
  • Elucidated a novel triclosan transport tunnel with cytosolic access.
  • Demonstrated that key residues are essential for efflux of triclosan, chloramphenicol, and pyrimethamine.

Conclusions:

  • The study provides a molecular basis for an unusual drug trafficking pathway utilized by RND efflux pumps.
  • This finding deepens our understanding of multidrug resistance mechanisms in Pseudomonas aeruginosa.
  • The identified transport mechanism offers potential targets for novel antimicrobial strategies.

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