Apoptosis-inducing factor (AIF), which is confined to mitochondria of normal healthy cells, is the first identified caspase-independent cell death effector. Moreover, AIF is required for the optimal functioning of the respiratory chain machinery. Recent findings have revealed that AIF fulfills its pro-survival function by interacting with CHCHD4, a soluble mitochondrial protein which promotes the entrance and the oxidative folding of different proteins in the inner membrane space. Here, we report the crystal structure of the ternary complex involving the N-terminal 27-mer peptide of CHCHD4, NAD, and AIF harboring its FAD (flavin adenine dinucleotide) prosthetic group in oxidized form. Combining this information with biophysical and biochemical data on the CHCHD4/AIF complex, we provide a detailed structural description of the interaction between the two proteins, validated by both chemical cross-linking mass spectrometry analysis and site-directed mutagenesis.

中文翻译：

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CHCHD4 结合影响凋亡诱导因子 (AIF) 的活性位点：变构调节的结构决定因素

凋亡诱导因子（AIF）仅限于正常健康细胞的线粒体，是第一个被识别的不依赖于半胱天冬酶的细胞死亡效应因子。此外，AIF 是呼吸链机械发挥最佳功能所必需的。最近的研究结果表明，AIF 通过与 CHCHD4 相互作用来实现其促生存功能，CHCHD4 是一种可溶性线粒体蛋白，可促进内膜空间中不同蛋白质的进入和氧化折叠。在这里，我们报告了三元复合物的晶体结构，该三元复合物涉及 CHCHD4、NAD 和 AIF 的 N 端 27 聚体肽，其中含有氧化形式的 FAD（黄素腺嘌呤二核苷酸）辅基。将这些信息与 CHCHD4/AIF 复合物的生物物理和生化数据相结合，我们提供了两种蛋白质之间相互作用的详细结构描述，并通过化学交联质谱分析和定点诱变进行了验证。