The Human Cytochrome c Domain-Swapped Dimer Facilitates Tight Regulation of Intrinsic Apoptosis
The Human Cytochrome c Domain-Swapped Dimer Facilitates Tight Regulation of Intrinsic Apoptosis
复制标题
人细胞色素 c 结构域交换二聚体促进内在细胞凋亡的严格调节
DOI：
10.1021/acs.biochem.0c00326
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发表时间：
2020
期刊：
影响因子：
2.9
通讯作者：
Bowler, Bruce E.
中科院分区：
文献类型：
--
作者：
Steele, Harmen B.;Elmer-Dixon, Margaret M.;Rogan, James T.;Ross, J. B.;Bowler, Bruce E.
细胞色素C（cytc）氧化心磷脂（CL）启动了细胞凋亡的内源性途径。结构域交换二聚体（DSD）的构象已被本实验室和其他实验室报道。DSD是cytc的替代构象体，可以在细胞凋亡早期氧化CL。我们在这里证明，cytcDSD有一组属性，将提供更严格的监管的内在途径。我们表明，人的DSD是动力学更稳定的马和酵母菌的DSD。圆二色性数据表明，DSD具有较少的不对称血红素环境，类似于当单体蛋白质以高脂质：蛋白质比率结合到CL囊泡时所看到的。二聚体在pH 7.0附近发生碱性构象转变，比单体低2.5个pH单位。从荧光相关光谱和荧光各向异性的数据表明，DSD的碱性过渡可以作为一个开关，从高亲和力CL nanodisces在pH 7.4到低得多的亲和力在pH 8.0。此外，人DSD的过氧化物酶活性在pH 7和8下比单体的过氧化物酶活性增加7倍，但在pH 6下当混合的Met 80/H2O连接取代碱性状态的赖氨酸连接时增加14倍。我们还提出的数据表明，cytcbinding显示出协同效应的cytcis的浓度增加。DSD似乎已经演变成pH诱导开关，其提供了控制pH 7.0附近的细胞凋亡激活的手段。
Oxidation of cardiolipin (CL) by cytochromec(cytc) has been proposed to initiate the intrinsic pathway of apoptosis. Domain-swapped dimer (DSD) conformations of cytchave been reported both by our laboratory and by others. The DSD is an alternate conformer of cytcthat could oxygenate CL early in apoptosis. We demonstrate here that the cytcDSD has a set of properties that would provide tighter regulation of the intrinsic pathway. We show that the human DSD is kinetically more stable than horse and yeast DSDs. Circular dichroism data indicate that the DSD has a less asymmetric heme environment, similar to that seen when the monomeric protein binds to CL vesicles at high lipid:protein ratios. The dimer undergoes the alkaline conformational transition near pH 7.0, 2.5 pH units lower than that of the monomer. Data from fluorescence correlation spectroscopy and fluorescence anisotropy suggest that the alkaline transition of the DSD may act as a switch from a high affinity for CL nanodiscs at pH 7.4 to a much lower affinity at pH 8.0. Additionally, the peroxidase activity of the human DSD increases 7-fold compared to that of the monomer at pH 7 and 8, but by 14-fold at pH 6 when mixed Met80/H2O ligation replaces the lysine ligation of the alkaline state. We also present data that indicate that cytcbinding shows a cooperative effect as the concentration of cytcis increased. The DSD appears to have evolved into a pH-inducible switch that provides a means to control activation of apoptosis near pH 7.0.