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From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins
Published on: July 4, 2016
Outer membrane active transport: structure of the BtuB:TonB complex
David D Shultis1, Michael D Purdy, Christian N Banchs
1Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.
Science (New York, N.Y.)
|June 3, 2006
Summary
Gram-negative bacteria use TonB-dependent transporters to import nutrients. This study reveals how TonB protein interacts with the cobalamin transporter BtuB, supporting a mechanical pulling mechanism for nutrient transport.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Gram-negative bacteria require outer membrane transporters for essential micronutrient uptake.
- Nutrient transport is powered by the proton-motive force across the inner membrane, coupled by the ExbB-ExbD-TonB complex.
- TonB protein directly interacts with transporters via a conserved Ton-box region.
Purpose of the Study:
- To elucidate the structural basis of TonB-mediated nutrient transport.
- To determine the structure of the cobalamin transporter BtuB in complex with TonB.
Main Methods:
- X-ray crystallography was used to solve the structure of the BtuB-TonB complex.
- Structural analysis focused on the interaction between the Ton-box of BtuB and the C-terminal domain of TonB.
Main Results:
- The Ton-box region of BtuB adopts a beta-strand conformation when bound to TonB.
- This beta-strand integrates into an existing beta-sheet structure within TonB.
- This structural rearrangement supports a model where TonB mechanically pulls the transporter.
Conclusions:
- The TonB-Ton-box interaction is crucial for coupling energy to outer membrane transport.
- The observed structure provides key insights into the mechanism of TonB-dependent transport.
- This finding advances our understanding of nutrient uptake in Gram-negative bacteria.
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