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Isolation of Physiologically Active Thylakoids and Their Use in Energy-Dependent Protein Transport Assays
Published on: September 28, 2018
TonB-dependent maltose transport by Caulobacter crescentus
S Lohmiller1,2, K Hantke2, S I Patzer1
1Max Planck Institute for Developmental Biology, Department of Protein Evolution, Tübingen, Germany.
Microbiology (Reading, England)
|June 6, 2008
Summary
Caulobacter crescentus utilizes a novel TonB-dependent system for maltose transport across its outer membrane. This energy-coupling mechanism involves MalA and a newly identified TonB protein, facilitating nutrient uptake.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Caulobacter crescentus utilizes maltodextrins as a carbon source.
- Outer membrane transport in bacteria often involves energy-coupling mechanisms.
Purpose of the Study:
- To elucidate the molecular mechanisms of maltose and maltodextrin transport in Caulobacter crescentus.
- To identify the specific proteins involved in energy-coupled transport across the outer and cytoplasmic membranes.
Main Methods:
- Genetic analysis involving gene deletion (exbB, exbD, tonB) to assess transport function.
- Site-directed mutagenesis of the TonB box in the MalA protein.
- Identification and characterization of genes within the mal locus.
Main Results:
- Deletion of a novel tonB gene (cc2334a) abolished maltose transport, indicating TonB dependence.
- MalA protein possesses a TonB box crucial for maltose uptake.
- MalY protein facilitates maltose transport across the cytoplasmic membrane.
- The mal locus encodes multiple proteins including amylases and regulators.
Conclusions:
- Caulobacter crescentus employs an energy-coupled, TonB-dependent system for outer membrane maltose transport.
- A previously unrecognized TonB protein is essential for this transport process.
- MalY mediates cytoplasmic membrane transport, likely via an ion-coupled mechanism.
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