Structural analysis of dynamins involved in mitochondrial morphology

除了发动蛋白，其他发动蛋白家族成员已经涉及各种基本细胞过程，包括线粒体分裂和融合、抗病毒活性、植物细胞板形成和叶绿体生物发生。在这些蛋白质中，自组装和寡聚成有序结构是一个共同的特征，对于大多数蛋白质来说，这对它们的功能至关重要。虽然有丰富的信息关于发动蛋白，很少有人知道发动蛋白相关的蛋白质的结构特性。近年来，我们研究了两个动力蛋白家族成员，一个参与线粒体分裂（Dnm 1），另一个参与线粒体融合，Opa 1。我们正在验证动力蛋白家族成员具有共同作用机制的假设。 我们的工作提供了明确的证据，动力蛋白相关的蛋白质具有相似的组装和GTdR特性。 然而，结构上的限制仍然必须考虑到它们广泛多样的生物功能。 发动蛋白家族的蛋白质由参与整个细胞的膜分裂和融合事件的独特GTP酶组成。我们的目标是了解这些蛋白质的动态结构特性，并将其与其不同的细胞功能相关联。发动蛋白是细胞内吞和囊泡形成所必需的。另外的动力蛋白家族成员涉及多种基本细胞过程，包括线粒体分裂和融合、抗病毒活性、细胞板形成和叶绿体生物发生。在这些蛋白质中，自组装和寡聚成有序结构是一个共同的特征，对于大多数蛋白质来说，这对它们的功能至关重要。虽然有丰富的信息关于发动蛋白，很少有人知道发动蛋白相关的蛋白质的结构特性。 为了确定动力蛋白家族成员之间是否存在共同的作用机制，我们研究了Dnm 1的结构和功能，Dnm 1是一种参与线粒体分裂的酵母动力蛋白家族成员，Opa 1是一种参与线粒体融合的人类动力蛋白。 在此之前，我们与加州理工学院的大卫陈博士合作，通过负染色和冷冻电子显微镜检查了OPA 1的结构。OPA 1（常染色体显性视神经萎缩）的突变可导致视网膜神经节细胞的遗传性神经病。在细胞中，OPA 1已被证明是线粒体内膜融合所必需的，但其作用机制仍然知之甚少。 向含有心磷脂的脂质体中添加OPA 1导致增强的GTP水解速率，并促进OPA 1在脂质周围自组装成螺旋阵列，形成蛋白质-脂质管。 目前，我们正通过螺旋和单粒子图像处理方法来解决OPA 1的结构。 GTP水解过程中OPA 1的构象状态也正在研究中。

In addition to dynamin, other dynamin family members have been implicated in a variety of fundamental cellular processes, including mitochondrial fission and fusion, anti-viral activity, plant cell plate formation and chloroplast biogenesis. Among these proteins, self-assembly and oligomerization into ordered structures is a common characteristic and, for the majority, is essential for their function. Although there is a wealth of information regarding dynamin, little is known about the structural properties of dynamin-related proteins. In recent years, we have examined two dynamin family members, one involved in mitochondria fission (Dnm1) and the other involved in mitochondrial fusion, Opa1. We are testing the hypothesis that dynamin family members share a common mechanism of action. Our work provides clear evidence that dynamin related proteins have similar assembly and GTPase properties. However, structural constraints must still allow for their widely diverse biological functions. The dynamin family of proteins consists of unique GTPases involved in membrane fission and fusion events throughout the cell. Our goal is to understand the dynamic structural properties of these proteins and correlate them with their diverse cellular functions. Dynamin is essential for endocytosis and vesiculation events in the cell. Additional dynamin family members have been implicated in a variety of fundamental cellular processes, including mitochondrial fission and fusion, anti-viral activity, cell plate formation and chloroplast biogenesis. Among these proteins, self-assembly and oligomerization into ordered structures is a common characteristic and, for the majority, is essential for their function. Although there is a wealth of information regarding dynamin, little is known about the structural properties of dynamin-related proteins. To determine if a common mechanism of action exists among the dynamin family members, we examined the structure and function of Dnm1, a yeast dynamin family member involved in mitochondria fission and Opa1, a human dynamin involved in mitochondria fusion. Previously, in collaboration with Dr. David Chan from Cal Tech, we examined the structure of OPA1 by negative stain and cryo electron microscopy. Mutations in OPA1 (autosomal dominant optic atrophy) can lead to an inherited neuropathy of the retinal ganglion cells. In the cell, OPA1 has been shown to be essential for the fusion of the inner mitochondrial membranes, but its mechanism of action remains poorly understood. Addition of OPA1 to liposomes containing cardiolipin results in enhanced GTP hydrolysis rate and promotes OPA1 to self-assemble into helical arrays around the lipid, forming protein-lipid tubes. Currently we are solving the structure of OPA1 by helical and single particle image processing methods. The conformational state of OPA1 during GTP hydrolysis is also being examined.