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Gewählte Publikation:

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Publikationstyp: Zeitschriftenaufsatz
Dokumenttyp: Originalarbeit

Jahr: 2003

AutorInnen: Urbánková, E; Voltchenko, A; Pohl, P; Jezek, P; Pohl, EE

Titel: Transport kinetics of uncoupling proteins. Analysis of UCP1 reconstituted in planar lipid bilayers.

Quelle: J Biol Chem. 2003; 278(35):32497-32500



Autor/innen der Vetmeduni Vienna:

Pohl Elena

Diese Publikation wurde nicht im Namen der Vetmeduni Vienna erstellt und ist deshalb ausschließlich der persönlichen Publikationsliste des/der Autors/Autorin zugeordnet!


Abstract:
According to alternative hypotheses, mitochondrial uncoupling protein 1 (UCP1) is either a proton channel ("buffering model") or a fatty acid anion carrier ("fatty acid cycling"). Transport across the proton channel along a chain of hydrogen bonds (Grotthus mechanism) may include fatty acid carboxyl groups or occur in the absence of fatty acids. In this work, we demonstrate that planar bilayers reconstituted with UCP1 exhibit an increase in membrane conductivity exclusively in the presence of fatty acids. Hence, we can exclude the hypothesis considering a preexisting H+ channel in UCP1, which does not require fatty acid for function. The augmented conductivity is nearly completely blocked by ATP. Direct application of transmembrane voltage and precise current measurements allowed determination of ATP-sensitive conductances at 0 and 150 mV as 11.5 and 54.3 pS, respectively, by reconstituting nearly 3 x 10(5) copies of UCP1. The proton conductivity measurements carried out in presence of a pH gradient (0.4 units) allowed estimation of proton turnover numbers per UCP1 molecule. The observed transport rate of 14 s-1 is compatible both with carrier and channel nature of UCP1.

Keywords Pubmed: Adenosine Triphosphate/metabolism
Animals
Carrier Proteins/chemistry*
Carrier Proteins/metabolism
Carrier Proteins/physiology*
Cricetinae
Dose-Response Relationship, Drug
Fatty Acids/metabolism*
Humans
Hydrogen Bonding
Hydrogen-Ion Concentration
Ion Channels
Kinetics
Lipid Bilayers/metabolism*
Membrane Potentials
Membrane Proteins/chemistry*
Membrane Proteins/metabolism
Membrane Proteins/physiology*
Mesocricetus
Mitochondrial Proteins
Oleic Acid/pharmacology
Protein Transport
Proteolipids/metabolism
Protons


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