EPR spectroscopy of 5-DOXYL-stearic acid bound to the mitochondrial uncoupling protein reveals its competitive displacement by alkylsulfonates in the channel and allosteric displacement by ATP.
Competition of fatty acids (FA) and alkylsulfonates with 5-DOXYL-stearic acid (5-SASL) binding to isolated mitochondrial uncoupling protein (UcP) is demonstrated using EPR spectroscopy. A distinct peak of the bound 5-SASL (h+1I) decreased with increasing concentration of competitors. Since alkylsulfonates are UcP substrates, it suggests that the FA binding site is located in the anion channel. Moreover, with increasing ATP the h+1I peak decreased and was smoothed with the 'micellar' peak into a single wider peak. A pH of 8.5 reversed this effect. It could reflect an allosteric release of 5-SASL from the ATP binding site which mimics the ATP gating mechanism.
Jezek
P
P
Department of Membrane Transport Biophysics, Academy of Sciences of the Czech Republic Videnská 1083, Prague.
Bauer
M
M
Trommer
W E
WE
D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000494:Allosteric Regulation; D000818:Animals; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism*; D006224:Cricetinae; D003497:Cyclic N-Oxides / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology; D007473:Ion Channels; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D008647:Mesocricetus; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D013113:Spin Labels; D013451:Sulfonic Acids / Q000494:pharmacology; D000071256:Uncoupling Protein 1
D002352:Carrier Proteins; D003497:Cyclic N-Oxides; D005230:Fatty Acids, Nonesterified; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D013113:Spin Labels; D013451:Sulfonic Acids; D000071256:Uncoupling Protein 1; C005072:5-doxylstearic acid