Cardiolipin (CL) is a mitochondrial anionic lipid that plays important roles in the regulation and signaling of mitochondrial apoptosis. CL peroxidation catalyzed by the assembly of CL-cytochrome c (cyt c) complexes at the inner mitochondrial membrane is a critical checkpoint. The structural changes in the protein, associated with peroxidase activation by CL and different anionic lipids, are not known at a molecular level. To better understand these peripheral protein-lipid interactions, we compare how phosphatidylglycerol (PG) and CL lipids trigger cyt c peroxidase activation, and correlate functional differences to structural and motional changes in membrane-associated cyt c. Structural and motional studies of the bound protein are enabled by magic angle spinning solid state NMR spectroscopy, while lipid peroxidase activity is assayed by mass spectrometry. PG binding results in a surface-bound state that preserves a nativelike fold, which nonetheless allows for significant peroxidase activity, though at a lower level than binding its native substrate CL. Lipid-specific differences in peroxidase activation are found to correlate to corresponding differences in lipid-induced protein mobility, affecting specific protein segments. The dynamics of omega loops C and D are upregulated by CL binding, in a way that is remarkably controlled by the protein:lipid stoichiometry. In contrast to complete chemical denaturation, membrane-induced protein destabilization reflects a destabilization of select cyt c foldons, while the energetically most stable helices are preserved. Our studies illuminate the interplay of protein and lipid dynamics in the creation of lipid peroxidase-active proteolipid complexes implicated in early stages of mitochondrial apoptosis.

中文翻译：

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细胞色素C过氧化物酶功能的激活通过与阴离子脂质相互作用时的协同Foldon环动力学。

心磷脂（CL）是一种线粒体阴离子脂质，在线粒体凋亡的调控和信号传导中起着重要作用。线粒体内膜上的CL-细胞色素c（cyt c）复合物的组装催化的CL过氧化是一个关键的检查点。在分子水平上，与CL和不同阴离子脂质激活的过氧化物酶相关的蛋白质结构变化尚不明确。为了更好地了解这些外周蛋白-脂质相互作用，我们比较了磷脂酰甘油（PG）和CL脂质如何触发cyt c过氧化物酶活化，并将功能差异与膜相关cyt c的结构和运动变化相关联。结合角蛋白的结构和运动研究可通过魔术角旋转固态NMR光谱进行，脂质过氧化物酶活性通过质谱分析。PG结合导致保留天然样折叠的表面结合状态，尽管其水平低于结合其天然底物CL的水平，但其仍允许显着的过氧化物酶活性。发现过氧化物酶活化中的脂质特异性差异与脂质诱导的蛋白质迁移率的相应差异相关，从而影响特定的蛋白质区段。ω环C和D的动力学通过CL结合而被上调，其方式明显受蛋白质：脂质化学计量学的控制。与完全化学变性相反，膜诱导的蛋白质去稳定反映了精选的Cyt c折叠的去稳定，而能量上最稳定的螺旋得以保留。