A model for drug transport across two membranes of Gram-negative bacteria by an MFS tripartite assembly

Related Experiment Video

Updated: Mar 18, 2026

In vitro Investigation of the MexAB Efflux Pump From Pseudomonas aeruginosa
13:40

In vitro Investigation of the MexAB Efflux Pump From Pseudomonas aeruginosa

Published on: February 17, 2014

12.3K

Zhaojun Zhong1, Tuerxunjiang Maimaiti1, Matthew L Jackson2,3

  • 1School of Life Science and Technology, ShanghaiTech University, Shanghai, China.

Nature Communications
|March 17, 2026
PubMed

Insights

Researchers elucidated the structure of a key bacterial efflux pump, EmrAB-TolC, revealing its assembly and drug transport mechanism. This finding advances understanding of antibiotic resistance in Gram-negative bacteria.

Area of Science:

  • Structural biology
  • Microbiology
  • Biochemistry

Background:

  • Bacterial cell envelope transport is vital for survival and antibiotic resistance.
  • Gram-negative bacteria require complex machinery for transport across dual membranes.
  • Major Facilitator Superfamily (MFS)-type tripartite efflux pumps are crucial for drug extrusion but their structure is poorly understood.

Purpose of the Study:

  • To determine the high-resolution structure of the EmrAB-TolC efflux pump.
  • To elucidate the assembly architecture and structural mechanism of MFS-type tripartite efflux pumps.
  • To identify key residues and functional mechanisms involved in multidrug transport.

Main Methods:

  • High-resolution cryo-electron microscopy (cryo-EM) to determine the structure of EmrAB-TolC.
  • Mutagenesis studies to identify essential residues for pump assembly and function.
  • Antibiotic sensitivity assays to validate the functional role of identified residues.

Main Results:

  • The high-resolution (3.13 Å) structure of the EmrAB-TolC pump was determined.
  • A distinct, asymmetric architecture was revealed with a TolC:EmrA:EmrB ratio of 3:6:1.
  • Essential contacts for pump assembly and key drug transport residues were identified.

Conclusions:

  • The study provides unprecedented structural insights into a representative MFS-type tripartite efflux pump.
  • Structural and functional data support a model for one-step drug transport across the Gram-negative bacterial envelope.
  • Findings contribute to understanding antibiotic resistance mechanisms and potential therapeutic targets.

More Related Videos

Expression, Detergent Solubilization, and Purification of a Membrane Transporter, the MexB Multidrug Resistance Protein10:43

Expression, Detergent Solubilization, and Purification of a Membrane Transporter, the MexB Multidrug Resistance Protein

Published on: December 3, 2010

23.0K
From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins09:55

From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins

Published on: July 4, 2016

14.2K

Related Concept Videos

Carrier-Mediated Transport01:06

Carrier-Mediated Transport

Carrier-mediated transport is a pivotal process in drug absorption, particularly for lipid-insoluble drugs, and encompasses facilitated diffusion and active transport. Facilitated diffusion allows drugs to move along their concentration gradient without energy expenditure, while active transport utilizes ATP to drive drug movement against this gradient.
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...
1.5K
Facilitated Diffusion01:16

Facilitated Diffusion

The plasma membrane, a critical structure in cellular biology, houses an array of transporters, or carrier proteins, interspersed within its lipid bilayer. These proteins play a crucial role in solute transport through facilitated diffusion, a form of passive diffusion that uses transporters to move the molecules across the membrane.
In this process, substrates such as organic compounds and ions interact with a transporter on one side, triggering conformational changes in proteins that enable...
1.5K
ABC Transporters: Importer01:27

ABC Transporters: Importer

ATP-binding cassette or ABC transporters are a class of ATP-driven pumps that hydrolyze ATP to move solutes across the membrane. They can be grouped into importers and exporters. While exporters are present in all domains of life, importers exist only in bacteria and some plants.
In bacteria, based on the number of transmembrane helices and the chemical nature of their substrates, the ABC importers can be divided into three types:
3.7K
Drug Absorption Mechanism: Carrier-Mediated Membrane Transport01:19

Drug Absorption Mechanism: Carrier-Mediated Membrane Transport

Certain large, lipid-insoluble drug molecules that resemble amino acids, peptides, or glucose, require specialized carrier proteins to facilitate their diffusion across cell membranes. This transport can occur through either facilitated diffusion, which does not require energy input, or active transport, which does require energy input.
Facilitated diffusion is a passive process that utilizes human Solute Carrier (SLC) transporters. These transporters bind to the drug, undergo structural...
6.8K
Structure of Porins01:21

Structure of Porins

Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a  motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel...
4.1K
ABC Transporters: Exporter01:31

ABC Transporters: Exporter

ATP-binding cassette or ABC transporter is the largest superfamily of integral membrane proteins. The transporters have transmembrane-binding domains (TMDs) and nucleotide-binding domains (NBDs). The TMDs are specific to their substrates, whereas the NBDs are similar to engines that complete ATP hydrolysis to complete the substrate transport. They can be full transporters consisting of two TMDs and NBDs, half transporters with one TMD and NBD, while some encoded with a single TMD or NBD are...
7.0K