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TonB and the gram-negative dilemma
1Department of Microbiology, Washington State University, Pullman 99164-4233.
Molecular Microbiology
|December 1, 1990
Summary
TonB protein powers nutrient transport in Gram-negative bacteria by linking inner membrane energy to outer membrane receptors. Its function is stabilized by ExbB and influenced by transport rates, with a model presented for its mechanism.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- TonB protein is crucial for active transport of nutrients like iron siderophores and vitamin B12 across the outer membrane of Gram-negative bacteria.
- It acts as an energy transducer, coupling the cytoplasmic membrane's energy to transport processes.
- The precise biochemical mechanism of this energy transduction is still under investigation.
Purpose of the Study:
- To elucidate the mechanism of TonB-dependent energy transduction.
- To describe the structural and functional interactions of TonB with other proteins involved in transport.
- To present a model for TonB function and regulation.
Main Methods:
- The study integrates existing biochemical and genetic data on TonB and associated proteins.
- A model is proposed based on known interactions and functional characteristics.
- Speculative elements are included to propose a comprehensive mechanism.
Main Results:
- TonB is anchored in the cytoplasmic membrane and extends into the periplasm to interact with outer membrane receptors.
- ExbB protein stabilizes TonB, and other proteins like ExbC, ExbD, and TolQ may also modulate its function.
- TonB's functional half-life is inversely related to the rate of active transport, shortening as transport increases.
Conclusions:
- TonB plays a vital role in nutrient uptake by Gram-negative bacteria.
- The interaction with ExbB and the modulation by transport rates are key aspects of TonB regulation.
- The presented model provides a framework for understanding TonB-mediated energy transduction and its regulation.