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Thermodynamic Basis for Conformational Coupling in an ATP-Binding Cassette Exporter
Katja Barth1,2, Michael Rudolph2,3, Tim Diederichs4
1Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt/Main, Germany.
The Journal of Physical Chemistry Letters
|August 21, 2020
Summary
This study reveals how ATP-binding cassette (ABC) transporters use entropy-enthalpy compensation for conformational changes. This mechanism powers substrate transport across membranes, crucial for cellular functions.
Area of Science:
- Biochemistry
- Structural Biology
- Membrane Protein Dynamics
Background:
- ATP-binding cassette (ABC) transporters are large protein superfamilies involved in transmembrane transport.
- The energy transduction mechanism from ATP to conformational changes in ABC transporters is not fully understood.
Purpose of the Study:
- To elucidate the thermodynamics of ATP-induced conformational switching in the ABC exporter TmrAB.
- To understand the energy coupling mechanism in ABC transporters.
Main Methods:
- Utilized temperature-resolved pulsed electron-electron double resonance (PELDOR or DEER) spectroscopy.
- Investigated the thermodynamics of nucleotide-binding domains (NBDs) and transmembrane domains (TMDs) in TmrAB.
Main Results:
- Identified a significant entropy-enthalpy compensation mechanism driving NBD closure.
- Observed mechanical coupling between NBD closure and outward TMD opening, associated with entropy gain.
- Highlighted the critical role of the conserved catalytic glutamate in the energetics.
Conclusions:
- The study reveals the thermodynamic basis for chemomechanical energy coupling in ABC exporters.
- Presents a novel strategy for investigating the energetics of membrane protein complexes.
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