Peroxidase activity and structural transitions of cytochrome c bound to cardiolipin-containing membranes
Peroxidase activity and structural transitions of cytochrome c bound to cardiolipin-containing membranes
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DOI：
10.1021/bi0525573
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发表时间：
2006-04-18
期刊：
影响因子：
2.9
通讯作者：
Kagan, VE
中科院分区：
文献类型：
--
作者：
Belikova, NA;Vladimirov, YA;Kagan, VE
在细胞凋亡过程中，细胞色素c （cyt c）从线粒体的膜间空间释放到细胞质中，在那里它触发半胱天冬酶依赖机制。我们发现，在细胞早期凋亡中，cyt c作为一种心磷脂（CL）特异性加氧酶发挥着另一个关键作用，产生促凋亡因子释放所需的CL氢过氧化物[Kagan， V. E., et al. (2005) Nat. Chem.]。生物工程学报，23(2):444 - 444。我们定量表征了CL和过氧化氢对cyt - c过氧化物酶活性的激活。在低离子强度和高CL/cyt - c比条件下，CL/cyt - c复合物的过氧化物酶活性提高了50倍。这种催化活性与TrP59荧光和695 nm (Fe-S（Met(80)）波段吸光度监测的cyt c部分展开相关。过氧化物酶活性的增加先于蛋白质三级结构的丧失。单不饱和四烯酰氯（TOCL）比饱和四烯酰氯（TMCL）更有效地诱导过氧化物酶活性和cyt c展开。发现TOCL/cyt - c复合物在高盐浓度下更能抵抗解离。这些发现表明，静电CL/cyt - c相互作用是启动过氧化物酶活性的核心，而当cyt - c的三级结构丢失时，则涉及疏水相互作用。在CL存在的情况下，cyt c过氧化物酶活性在较低的H2O2浓度下被激活，而不是单独的cyt c分子。这表明，线粒体膜上CL的重新分配结合H2O2的增加可以开启cyt - c过氧化物酶活性和线粒体中CL的氧化-这是细胞凋亡的必要步骤。
During apoptosis, cytochrome c (cyt c) is released from intermembrane space of mitochondria into the cytosol where it triggers the caspase-dependent machinery. We discovered that cyt c plays another critical role in early apoptosis as a cardiolipin (CL)-specific oxygenase to produce CL hydroperoxides required for release of pro-apoptotic factors [Kagan, V. E., et al. (2005) Nat. Chem. Biol. 1, 223-232]. We quantitatively characterized the activation of peroxidase activity of cyt c by CL and hydrogen peroxide. At low ionic strength and high CL/cyt c ratios, peroxidase activity of the CL/cyt c complex was increased >50 times. This catalytic activity correlated with partial unfolding of cyt c monitored by TrP59 fluorescence and absorbance at 695 nm (Fe-S(Met(80)) band). The peroxidase activity increase preceded the loss of protein tertiary structure. Monounsaturated tetraoleoyl-CL (TOCL) induced peroxidase activity and unfolding of cyt c more effectively than saturated tetramyristoyl-CL (TMCL). TOCL/cyt c complex was found more resistant to dissociation by high salt concentration. These findings suggest that electrostatic CL/cyt c interactions are central to the initiation of the peroxidase activity, while hydrophobic interactions are involved when cyt c's tertiary structure is lost. In the presence of CL, cyt c peroxidase activity is activated at lower H2O2 concentrations than for isolated cyt c molecules. This suggests that redistribution of CL in the mitochondrial membranes combined with increased production of H2O2 can switch on the peroxidase activity of cyt c and CL oxidation in mitochondria-a required step in execution of apoptosis.