The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge, United Kingdom.
The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge, United Kingdom.
J Biol Chem. 2024 Mar;300(3):105690. doi: 10.1016/j.jbc.2024.105690. Epub 2024 Jan 26.
The hydrolytic activity of the ATP synthase in bovine mitochondria is inhibited by a protein called IF, but bovine IF has no effect on the synthetic activity of the bovine enzyme in mitochondrial vesicles in the presence of a proton motive force. In contrast, it has been suggested based on indirect observations that human IF inhibits both the hydrolytic and synthetic activities of the human ATP synthase and that the activity of human IF is regulated by the phosphorylation of Ser-14 of mature IF. Here, we have made both human and bovine IF which are 81 and 84 amino acids long, respectively, and identical in 71.4% of their amino acids and have investigated their inhibitory effects on the hydrolytic and synthetic activities of ATP synthase in bovine submitochondrial particles. Over a wide range of conditions, including physiological conditions, both human and bovine IF are potent inhibitors of ATP hydrolysis, with no effect on ATP synthesis. Also, substitution of Ser-14 with phosphomimetic aspartic and glutamic acids had no effect on inhibitory properties, and Ser-14 is not conserved throughout mammals. Therefore, it is unlikely that the inhibitory activity of mammalian IF is regulated by phosphorylation of this residue.
牛线粒体中的 ATP 合酶的水解活性被一种称为 IF 的蛋白质抑制，但在质子动力存在的情况下，牛 IF 对线粒体囊泡中牛酶的合成活性没有影响。相比之下，根据间接观察结果表明，人 IF 抑制人 ATP 合酶的水解和合成活性，并且人 IF 的活性受到成熟 IF 的 Ser-14 磷酸化的调节。在这里，我们分别制备了 81 个和 84 个氨基酸长的人 IF 和牛 IF，并且它们在 71.4%的氨基酸上是相同的，并研究了它们对牛亚线粒体颗粒中 ATP 合酶的水解和合成活性的抑制作用。在包括生理条件在内的广泛条件下，人 IF 和牛 IF 都是 ATP 水解的有效抑制剂，对 ATP 合成没有影响。此外，用磷酸模拟天冬氨酸和谷氨酸取代 Ser-14 对抑制特性没有影响，并且 Ser-14 在整个哺乳动物中没有保守。因此，哺乳动物 IF 的抑制活性不太可能通过该残基的磷酸化来调节。
