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A Proteoliposome-Based Efflux Assay to Determine Single-molecule Properties of Cl- Channels and Transporters
Published on: April 20, 2015
The structural basis of modularity in ECF-type ABC transporters
Guus B Erkens1, Ronnie P-A Berntsson, Faizah Fulyani
1University of Groningen, Groningen Biomolecular Science and Biotechnology Institute, Groningen, The Netherlands.
Nature Structural & Molecular Biology
|June 28, 2011
Summary
Energy coupling factor (ECF) transporters facilitate vitamin uptake in prokaryotes. The crystal structure of thiamine transporter ThiT reveals key interactions, proposing a general transport mechanism for ECF transporters.
Area of Science:
- Structural biology
- Microbiology
- Biochemistry
Background:
- Energy coupling factor (ECF) transporters are crucial for prokaryotic vitamin uptake.
- These transporters comprise a substrate-specific S-component and an energizing module linked to ABC transporters.
- Diverse S-components often lack sequence similarity but utilize the same energizing module.
Purpose of the Study:
- To determine the crystal structure of the thiamine-specific S-component, ThiT, from Lactococcus lactis.
- To elucidate the molecular basis for high-affinity thiamine binding by ThiT.
- To propose a general transport mechanism for ECF transporters.
Main Methods:
- X-ray crystallography to obtain the crystal structure of ThiT at 2.0 Å resolution.
- Analysis of protein-substrate interactions to understand binding affinity.
- Comparative structural analysis with other S-components like RibU.
Main Results:
- The crystal structure of ThiT reveals extensive interactions responsible for its high affinity for thiamine (K(d) ~10(-10) M).
- ThiT shares a similar fold with the riboflavin transporter RibU, despite only 14% sequence identity.
- A conserved AxxxA motif with two alanine residues mediates interaction with the energizing module.
Conclusions:
- The structural insights into ThiT provide a detailed understanding of thiamine transport.
- A conserved structural motif (AxxxA) is critical for ECF transporter function.
- A general transport mechanism for ECF transporters can be proposed based on these findings.
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