Jarmuszkiewicz Wieslawa, Swida Aleksandra, Czarna Malgorzata, Antos Nina, Sluse-Goffart Claudine M, Sluse Francis E
Laboratory of Bioenergetics, Adam Mickiewicz University, Fredry 10, 61-701 Poznan, Poland.
J Bioenerg Biomembr. 2005 Apr;37(2):97-107. doi: 10.1007/s10863-005-4133-y.
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.
在分离的以外部NADH或琥珀酸为底物进行状态3呼吸的卡氏棘阿米巴线粒体中，亚油酸诱导的嘌呤核苷酸敏感解偶联蛋白活性能够使氧化磷酸化解偶联。当醌（Q）充分氧化时，嘌呤核苷酸（GTP）可抑制亚油酸诱导的解偶联，这表明在进行状态3呼吸的卡氏棘阿米巴线粒体中，解偶联蛋白活性对GTP的敏感性取决于膜结合Q的氧化还原状态。也就是说，在未受抑制的状态3呼吸以及被复合物III抑制剂逐步抑制的状态3呼吸中，即当喹醇（QH₂）氧化途径的速率降低时，未观察到GTP对亚油酸诱导的解偶联的抑制作用。相反，通过降低呼吸底物可用性（通过限制琥珀酸摄取或降低外部NADH浓度），即当Q还原途径的速率降低时，状态3呼吸的逐步降低会逐渐导致GTP产生完全抑制作用。此外，在从冷处理细胞中分离的卡氏棘阿米巴线粒体中，观察到更高的解偶联蛋白活性，对于相同的低Q还原水平值，GTP可抑制亚油酸诱导的质子泄漏。
