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Origin and Evolution of Bacterial Periplasmic Force Transducers
Daniel P Williams-Jones1, Melissa N Webby1, James E Bray2
1Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
Molecular Biology and Evolution
|June 21, 2025
Summary
Researchers traced the evolutionary origins of bacterial outer membrane proteins TolA and TonB using structural predictions. They discovered TolA likely evolved from TonB and identified novel force-transducing systems and outer membrane-tethering mechanisms.
Area of Science:
- Microbiology
- Evolutionary Biology
- Structural Biology
Background:
- Double-membraned bacteria utilize coupled inner and outer membrane processes.
- TolA and TonB proteins link inner membrane energy to outer membrane functions like stabilization and import.
- Low sequence conservation hinders understanding the evolution of these force-transducing proteins.
Purpose of the Study:
- To elucidate the evolutionary trajectories and origins of TolA and TonB proteins.
- To identify and annotate force transduction operons using structural prediction.
- To trace the distribution and evolutionary history of these systems in bacteria.
Main Methods:
- Utilized structural prediction approaches to analyze protein families.
- Identified and annotated force transduction operons across diverse bacterial taxa.
- Compared the distribution of Tol-Pal and Ton systems.
Main Results:
- Identified a novel outer membrane-tethering system and a new family of monomeric force transducers.
- Revealed the core organizational principles of the tol-pal operon in various bacteria.
- Found the TolA’s α-helical domain II structure is anomalous, prevalent mainly in γ-proteobacteria.
- Suggested TolA evolved from a TonB paralogue and co-emerged with Pal.
- Determined TolB likely originated from outer membrane proteins and CpoB was an ancestral lipoprotein.
Conclusions:
- The Tol-Pal system is extensively conserved in Gracilicutes, underscoring its importance in bacterial cell biology.
- Structural prediction is a powerful tool for tracing the evolution of conserved protein systems.
- The study reveals novel insights into the co-evolution of essential bacterial outer membrane protein systems.
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