title: Fatty acids change the conformation of uncoupling protein 1 (UCP1).
abstract: UCP1 catalyzes proton leak across the mitochondrial inner membrane to disengage substrate oxidation from ATP production. It is well established that UCP1 is activated by fatty acids and inhibited by purine nucleotides, but precisely how this regulation occurs remains unsettled. Although fatty acids can competitively overcome nucleotide inhibition in functional assays, fatty acids have little effect on purine nucleotide binding. Here, we present the first demonstration that fatty acids induce a conformational change in UCP1. Palmitate dramatically changed the binding kinetics of 2'/3'-O-(N-methylanthraniloyl)-GDP, a fluorescently labeled nucleotide analog, for UCP1. Furthermore, palmitate accelerated the rate of enzymatic proteolysis of UCP1. The altered kinetics of both processes indicate that fatty acids change the conformation of UCP1, reconciling the apparent discrepancy between existing functional and ligand binding data. Our results provide a framework for how fatty acids and nucleotides compete to regulate the activity of UCP1.
authors.affiliation: Medical Research Council Mitochondrial Biology Unit, Cambridge CB2 0XY, United Kingdom. adivakaruni@ucsd.edu
authors.forename: Ajit S
authors.initials: AS
authors.lastname: Divakaruni
authors.forename: Dickon M
authors.initials: DM
authors.lastname: Humphrey
authors.forename: Martin D
authors.initials: MD
authors.lastname: Brand
mesh_terms: D002001:Adipose Tissue, Brown / Q000166:cytology; D000818:Animals; D001667:Binding, Competitive; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D010168:Palmitates / Q000494:pharmacology*; D011485:Protein Binding; D011487:Protein Conformation; D059748:Proteolysis; D051381:Rats; D017208:Rats, Wistar; D013950:Thymus Gland / Q000166:cytology; D014357:Trypsin / Q000737:chemistry; D000071256:Uncoupling Protein 1; D062367:ortho-Aminobenzoates / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes; D007473:Ion Channels; D024101:Mitochondrial Proteins; D010168:Palmitates; C000604372:Ucp1 protein, mouse; C000604373:Ucp1 protein, rat; D000071256:Uncoupling Protein 1; D062367:ortho-Aminobenzoates; C065197:3'-(methylanthraniloyl)-2'-deoxy-guanosine diphosphate; D006153:Guanosine Diphosphate; D014357:Trypsin