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Uncoupling protein, H+ transport and regulation.
M Klingenberg1, E Winkler, K Echtay
1Institute of Physical Biochemistry, University of Munich, Schillerstrasse 44, D-80336 Munich, Germany. klingenberg@pbm.med.uni-muenchen.de
Biochemical Society Transactions
|November 16, 2001
Summary
Coenzyme Q is essential for uncoupling protein (UCP) function, enabling proton transport crucial for energy metabolism. This cofactor, along with fatty acids, facilitates H+ transport through UCP channels.
Area of Science:
- Biochemistry
- Molecular Biology
- Mitochondrial Physiology
Background:
- Uncoupling proteins (UCPs) regulate mitochondrial proton leak and energy expenditure.
- UCP1 serves as a model, but studying other UCPs like UCP3 presents challenges due to expression and localization issues.
Purpose of the Study:
- To elucidate the biochemical functions of uncoupling proteins (UCPs), focusing on the role of coenzyme Q.
- To overcome challenges in studying UCP3 function by developing a reconstituted system.
Main Methods:
- Heterologous expression of UCPs in yeast and Escherichia coli.
- Incorporation of purified UCPs into vesicles for transport assays.
- Reconstitution of proton (H+) transport with and without coenzyme Q and fatty acids.
Main Results:
- Heterologous expression of UCP3 in yeast led to extra-mitochondrial deposits, hindering functional studies.
- Purified UCPs in vesicles showed only chloride (Cl-) transport, not proton (H+) transport.
- Coenzyme Q addition reconstituted nucleotide-sensitive H+ transport for UCP1, UCP2, and UCP3.
Conclusions:
- Coenzyme Q acts as a crucial cofactor for proton transport by UCPs.
- A proposed mechanism involves coenzyme Q and fatty acids cooperating to inject H+ into the UCP channel.
- This finding provides a new avenue for studying UCP function and regulation.