How Bacteria Take Up Dipeptides: New Structural Insights

Greg Howard
10th March, 2025

How Bacteria Take Up Dipeptides: New Structural Insights

The periplasmic scoop motif of DppB in Escherichia coli is essential for efficient dipeptide import, as shown by bacterial complementation assays (c) and ATPase activity measurements (d) demonstrating that mutations disrupting the scoop loop–DppA interaction or deletion of the scoop motif impair substrate transport, likely by failing to seal the outward-facing cavity and prevent dipeptide escape into the periplasm (e).

Image adapted from: Li et al. / CC BY (Source)

Key Findings

  • Scientists in Beijing uncovered how a crucial protein in E. coli helps the bacteria take in nutrients and resist antibiotics
  • They discovered that this protein requires both a specific binding partner and energy to function, controlling substance movement into the cell
  • These insights may lead to new antibiotics that block the protein, helping to fight antibiotic-resistant bacteria
ABC transporters are essential proteins found in all forms of life, playing crucial roles in moving a variety of substances across cellular membranes. In bacteria, these transporters are involved in processes that contribute to disease and antibiotic resistance[2]. A recent study from the Chinese Academy of Sciences in Beijing[1] has shed new light on how a specific ABC transporter in Escherichia coli functions, providing insights that could influence the development of new antibiotics. The study focused on the dipeptide transporter DppABCDF, a member of the ABC transporter family found in Gram-negative bacteria. ABC transporters like DppABCDF are responsible for importing essential molecules such as amino acids and peptides into the bacterial cell, as well as exporting substances that can contribute to virulence and antibiotic resistance[2]. Understanding the structure and mechanism of these transporters is vital for developing strategies to combat antibiotic-resistant bacteria. Using advanced cryo-electron microscopy (cryo-EM), the researchers visualized the structure of the DppBCDF translocator complex in both its inactive (apo) form and when bound to ATP analogs that mimic the energy state required for transport. They also examined the full DppABCDF transporter bound to ATPγS, a slowly hydrolyzable ATP analog. These structural insights revealed that the DppBCDF translocator exists as a heterotetramer in E. coli, differing from similar transporters in other bacteria like Mycobacterium tuberculosis. One of the key findings was that the DppBCDF translocator remains inactive on its own and requires the binding of both the substrate-binding protein DppA and ATP to become active. This activation results in a conformational change from an inward-facing to an outward-facing state, allowing the transporter to move dipeptides into the cell. Additionally, the study identified a unique periplasmic scoop motif in the DppB subunit. This motif likely plays a critical role in ensuring that dipeptides are efficiently imported without leaking back out or escaping into the periplasm, the space between the bacterial inner and outer membranes. These structural and functional discoveries build upon previous research into ABC transporters and antibiotic uptake mechanisms. For instance, studies on negamycin, an antibiotic that utilizes peptide transporters to enter bacterial cells, have shown that multiple transport routes can contribute to its effectiveness and low resistance rates[3]. Similarly, research on pacidamycins highlighted how mutations in peptide transport systems can lead to high-frequency antibiotic resistance by impairing drug uptake[4]. The current study's detailed depiction of the DppABCDF transporter advances our understanding of how these transport systems operate at a molecular level, which is essential for addressing antibiotic resistance. By elucidating the structure and activation mechanism of DppABCDF, the research provides potential targets for new antibiotics that could inhibit transporter function, thereby preventing bacteria from importing essential nutrients or exporting toxic compounds. Moreover, the identification of the periplasmic scoop motif offers a specific feature that drug developers might exploit to disrupt transporter efficiency. The findings also have broader implications for the role of ABC transporters in bacterial virulence and pathogenesis. Since these transporters are involved in importing nutrients necessary for bacterial survival and exporting factors that contribute to disease, targeting them could weaken pathogenic bacteria and make them more susceptible to existing antibiotics[2]. Additionally, understanding transporter mechanisms can aid in designing drugs that are less likely to encounter resistance, as seen with negamycin's diverse uptake pathways[3]. Overall, the study from the Chinese Academy of Sciences provides a comprehensive view of the DppABCDF transporter in E. coli, enhancing our knowledge of bacterial ABC transporters and their role in antibiotic resistance. This research not only advances the fundamental understanding of transporter biology but also paves the way for developing novel therapeutic strategies to combat resistant bacterial infections.

BiotechBiochem

References

Main Study

1) Structural characterization of the ABC transporter DppABCDF in Escherichia coli reveals insights into dipeptide acquisition

Published 7th March, 2025

https://doi.org/10.1371/journal.pbio.3003026

Related Studies

2) The role of bacterial ATP-binding cassette (ABC) transporters in pathogenesis and virulence: Therapeutic and vaccine potential.

https://doi.org/10.1016/j.micpath.2022.105734

3) The Antibiotic Negamycin Crosses the Bacterial Cytoplasmic Membrane by Multiple Routes.

https://doi.org/10.1128/AAC.00986-20

4) High-level pacidamycin resistance in Pseudomonas aeruginosa is mediated by an opp oligopeptide permease encoded by the opp-fabI operon.

https://doi.org/10.1128/AAC.01198-13


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