Nishida Keiji, Yagisawa Fumi, Kuroiwa Haruko, Yoshida Yamato, Kuroiwa Tsuneyoshi
Laboratory of Cell Biology, Department of Life Science, College of Science, Rikkyo (St. Paul's) University, Toshima, Tokyo 171-8501, Japan.
Proc Natl Acad Sci U S A. 2007 Mar 13;104(11):4736-41. doi: 10.1073/pnas.0609364104. Epub 2007 Mar 1.
Mitochondria are not produced de novo but are maintained by division. Mitochondrial division is a coordinated process of positioning and constriction of the division site and fission of double membranes, in which dynamin-related protein is believed to mediate outer membrane fission. Part of the mitochondrial division machinery was purified from M phase-arrested Cyanidioschyzon merolae cells through biochemical fractionation. The dynamin-related protein Dnm1 was one of the two major proteins in the purified fraction and was accompanied by a newly identified protein CMR185C, named Mda1. Mda1 contained a predictable coiled-coil region and WD40 repeats, similarly to Mdv1 and Caf4 in yeasts. Immunofluorescence and immunoelectron microscopy showed that Mda1 localizes as a medial belt or ring on the mitochondrial outer surface throughout the division. The ring formation of Mda1 followed the plane of the ring of FtsZ, a protein that resides in the matrix. Dnm1 consistently colocalized with Mda1 only in the late stages of division. Mda1 protein was expressed through S to M phases and was phosphorylated specifically in M phase when Mda1 transformed from belt into foci and became colocalizing with Dnm1. Dephosphorylation of Mda1 in vitro increased its sedimentation coefficient, suggesting conformational changes of the macromolecule. Disassembly of the purified mitochondrial division machinery was performed by adding GTP to independently release Dnm1, suggesting that Mda1 forms a stable homo-oligomer by itself as a core structure of the mitochondrial division machinery.
线粒体并非重新产生，而是通过分裂来维持。线粒体分裂是一个涉及分裂位点定位与收缩以及双膜裂变的协调过程，其中动力蛋白相关蛋白被认为介导外膜裂变。线粒体分裂机制的一部分是通过生化分级分离从处于M期阻滞的梅氏嗜热栖热菌细胞中纯化得到的。动力蛋白相关蛋白Dnm1是纯化组分中的两种主要蛋白质之一，同时还伴随着一种新鉴定的蛋白质CMR185C，命名为Mda1。Mda1含有可预测的卷曲螺旋区域和WD40重复序列，类似于酵母中的Mdv1和Caf4。免疫荧光和免疫电子显微镜显示，Mda1在整个分裂过程中定位于线粒体外表面的中间带或环上。Mda1的环形成遵循FtsZ环的平面，FtsZ是一种存在于基质中的蛋白质。Dnm1仅在分裂后期与Mda1始终共定位。Mda1蛋白在S期到M期表达，并且在M期当Mda1从带形转变为焦点并与Dnm1共定位时发生特异性磷酸化。体外Mda1的去磷酸化增加了其沉降系数，表明该大分子发生了构象变化。通过添加GTP进行纯化的线粒体分裂机制的拆解，以独立释放Dnm1，这表明Mda1自身形成稳定的同型寡聚体，作为线粒体分裂机制的核心结构。
