title: In phosphorylating Acanthamoeba castellanii mitochondria the sensitivity of uncoupling protein activity to GTP depends on the redox state of quinone.
abstract: In isolated Acanthamoeba castellanii mitochondria respiring in state 3 with external NADH or succinate, the linoleic acid-induced purine nucleotide-sensitive uncoupling protein activity is able to uncouple oxidative phosphorylation. The linoleic acid-induced uncoupling can be inhibited by a purine nucleotide (GTP) when quinone (Q) is sufficiently oxidized, indicating that in A. castellanii mitochondria respiring in state 3, the sensitivity of uncoupling protein activity to GTP depends on the redox state of the membranous Q. Namely, the inhibition of the linoleic acid-induced uncoupling by GTP is not observed in uninhibited state 3 respiration as well as in state 3 respiration progressively inhibited by complex III inhibitors, i.e., when the rate of quinol (QH(2))-oxidizing pathway is decreased. On the contrary, the progressive decrease of state 3 respiration by declining respiratory substrate availability (by succinate uptake limitation or by decreasing external NADH concentration), i.e., when the rate of Q-reducing pathways is decreased, progressively leads to a full inhibitory effect of GTP. Moreover, in A. castellanii mitochondria isolated from cold-treated cells, where a higher uncoupling protein activity is observed, the inhibition of the linoleic acid-induced proton leak by GTP is revealed for the same low values of the Q reduction level.
authors.affiliation: Laboratory of Bioenergetics, Adam Mickiewicz University, Fredry 10, 61-701 Poznan, Poland. wiesiaj@amu.edu.pl
authors.forename: Wieslawa
authors.initials: W
authors.lastname: Jarmuszkiewicz
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Swida
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Czarna
authors.forename: Nina
authors.initials: N
authors.lastname: Antos
authors.forename: Claudine M
authors.initials: CM
authors.lastname: Sluse-Goffart
authors.forename: Francis E
authors.initials: FE
authors.lastname: Sluse
mesh_terms: D048248:Acanthamoeba castellanii / Q000378:metabolism*; D000818:Animals; D016227:Benzoquinones / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D007473:Ion Channels; D007700:Kinetics; D019787:Linoleic Acid / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D024101:Mitochondrial Proteins; D010084:Oxidation-Reduction; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption; D012987:Soil / Q000469:parasitology; D000071256:Uncoupling Protein 1
chemical_list: D016227:Benzoquinones; D002352:Carrier Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D012987:Soil; D000071256:Uncoupling Protein 1; C004532:quinone; D006160:Guanosine Triphosphate; D019787:Linoleic Acid