PDF(Pubmed)
Abstract：
Mitofusins (Mfn1 and Mfn2) are the mitochondrial outer-membrane fusion proteins in mammals and belong to the dynamin superfamily of multidomain GTPases. Recent structural studies of truncated variants lacking alpha helical transmembrane domains suggested that Mfns dimerize to promote the approximation and the fusion of the mitochondrial outer membranes upon the hydrolysis of guanine 5\'-triphosphate disodium salt (GTP). However, next to the presence of GTP, the fusion activity seems to require multiple regulatory factors that control the dynamics and kinetics of mitochondrial fusion through the formation of Mfn1-Mfn2 heterodimers. Here, we purified and reconstituted the full-length murine Mfn2 protein into giant unilamellar vesicles (GUVs) with different lipid compositions. The incubation with GTP resulted in the fusion of Mfn2-GUVs. High-speed video-microscopy showed that the Mfn2-dependent membrane fusion pathway progressed through a zipper mechanism where the formation and growth of an adhesion patch eventually led to the formation of a membrane opening at the rim of the septum. The presence of physiological concentration (up to 30 mol%) of dioleoyl-phosphatidylethanolamine (DOPE) was shown to be a requisite to observe GTP-induced Mfn2-dependent fusion. Our observations show that Mfn2 alone can promote the fusion of micron-sized DOPE-enriched vesicles without the requirement of regulatory cofactors, such as membrane curvature, or the assistance of other proteins.
摘要：
线粒体蛋白（Mfn1和Mfn2）是哺乳动物中的线粒体外膜融合蛋白，属于多结构域GTP酶的动态蛋白超家族。最近缺乏α螺旋跨膜结构域的截短变体的结构研究表明，Mfns二聚化以促进鸟嘌呤5'-三磷酸二钠盐（GTP）水解后线粒体外膜的近似和融合。然而,除了GTP的存在，融合活性似乎需要多种调节因子，通过形成Mfn1-Mfn2异二聚体来控制线粒体融合的动力学和动力学。这里,我们纯化了全长鼠Mfn2蛋白，并将其重建为具有不同脂质组成的巨大单层囊泡（GUV）。与GTP的孵育导致Mfn2-GUV的融合。高速视频显微镜显示，依赖Mfn2的膜融合途径通过拉链机制进行，其中粘附斑的形成和生长最终导致在隔膜边缘形成膜开口。生理浓度（高达30mol％）的二油酰基-磷脂酰乙醇胺（DOPE）的存在被证明是观察GTP诱导的Mfn2依赖性融合的必要条件。我们的观察表明，单独的Mfn2可以促进微米大小的富含DOPE的囊泡的融合，而不需要调节辅因子，如膜曲率，或其他蛋白质的帮助。
