Dnm1 and Fis1 are prototypical proteins that regulate yeast mitochondrial morphology by controlling fission, the dysregulation of which can result in developmental disorders and neurodegenerative diseases in humans. Loss of Dnm1 blocks the formation of fission complexes and leads to elongated mitochondria in the form of interconnected networks, while overproduction of Dnm1 results in excessive mitochondrial fragmentation. In the current model, Dnm1 is essentially a GTP hydrolysis-driven molecular motor that self-assembles into ring-like oligomeric structures that encircle and pinch the outer mitochondrial membrane at sites of fission. In this work, we use machine learning and synchrotron small-angle X-ray scattering (SAXS) to investigate whether the motor Dnm1 can synergistically facilitate mitochondrial fission by membrane remodeling. A support vector machine (SVM)-based classifier trained to detect sequences with membrane-restructuring activity identifies a helical Dnm1 domain capable of generating negative Gaussian curvature (NGC), the type of saddle-shaped local surface curvature found on scission necks during fission events. Furthermore, this domain is highly conserved in Dnm1 homologues with fission activity. Synchrotron SAXS measurements reveal that Dnm1 restructures membranes into phases rich in NGC, and is capable of inducing a fission neck with a diameter of 12.6 nm. Through in silico mutational analysis, we find that the helical Dnm1 domain is locally optimized for membrane curvature generation, and phylogenetic analysis suggests that dynamin superfamily proteins that are close relatives of human dynamin Dyn1 have evolved the capacity to restructure membranes via the induction of curvature mitochondrial fission. In addition, we observe that Fis1, an adaptor protein, is able to inhibit the pro-fission membrane activity of Dnm1, which points to the antagonistic roles of the two proteins in the regulation of mitochondrial fission.

中文翻译：

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分子电动机Dnm1协同诱导膜曲率，以促进线粒体裂变

Dnm1和Fis1是通过控制裂变来调节酵母线粒体形态的原型蛋白，其失调可导致人类发育障碍和神经退行性疾病。Dnm1的丢失会阻止裂变复合物的形成，并导致相互连接的网络形式的线粒体伸长，而Dnm1的过量生产会导致线粒体过度断裂。在当前模型中，Dnm1本质上是由GTP水解驱动的分子电动机，其自身组装成环状的寡聚结构，该结构在裂变部位围绕并挤压线粒体外膜。在这项工作中，我们使用机器学习和同步加速器小角度X射线散射（SAXS）来研究电机Dnm1是否可以通过膜重塑协同促进线粒体裂变。基于支持向量机（SVM）的分类器经过训练可检测具有膜重组活性的序列，可识别能够产生负高斯曲率（NGC）的螺旋Dnm1域，该高斯曲率是裂变事件中在断颈上发现的鞍形局部表面曲率的类型。此外，该结构域在具有裂变活性的Dnm1同源物中高度保守。同步加速器SAXS测量显示Dnm1将膜重组为富含NGC的相，并能够诱发直径为12.6 nm的裂变颈。通过 此外，该结构域在具有裂变活性的Dnm1同源物中高度保守。同步加速器SAXS测量显示Dnm1将膜重组为富含NGC的相，并能够诱发直径为12.6 nm的裂变颈。通过 此外，该结构域在具有裂变活性的Dnm1同源物中高度保守。同步加速器SAXS测量显示Dnm1将膜重组为富含NGC的相，并能够诱发直径为12.6 nm的裂变颈。通过在计算机突变分析中，我们发现螺旋形Dnm1结构域已针对膜曲率产生进行了局部优化，并且系统发育分析表明，与人dynamin Dyn1密切相关的dynamin超家族蛋白已通过诱导曲率线粒体裂变而进化了重组膜的能力。 。此外，我们观察到，衔接蛋白Fis1能够抑制Dnm1的裂变膜活性，这表明这两种蛋白在调节线粒体裂变中具有拮抗作用。