Hoogenboom Bart W, Suda Kitaru, Engel Andreas, Fotiadis Dimitrios
M. E. Müller Institute for Microscopy, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
J Mol Biol. 2007 Jul 6;370(2):246-55. doi: 10.1016/j.jmb.2007.04.073. Epub 2007 May 10.
Voltage-dependent anion channels (VDACs) are major constituents of the outer mitochondrial membrane (OMM). These primary transporters of nucleotides, ions and metabolites mediate a substantial portion of the OMM molecular traffic. To study the native supramolecular organization of the VDAC, we have isolated, characterized and imaged OMMs from potato tubers. SDS-PAGE and mass spectrometry of OMMs revealed the presence of the VDAC isoforms POM34 and POM36, as well as the translocase of the OMM complex. Tubular two-dimensional crystals of the VDAC spontaneously formed after incubation of OMMs for two to three months at 4 degrees C. Transmission electron microscopy revealed an oblique lattice and unit cells housing six circular depressions arranged in a hexagon. Atomic force microscopy of freshly isolated OMMs demonstrated (i) the existence of monomers to tetramers, hexamers and higher oligomers of the VDAC and (ii) its spatial arrangement within the oligomers in the native membrane. We discuss the importance of the observed oligomerization for modulation of the VDAC function, for the binding of hexokinase and creatine kinase to the OMM and for mitochondria-mediated apoptosis.
电压依赖性阴离子通道（VDACs）是线粒体外膜（OMM）的主要组成部分。这些核苷酸、离子和代谢物的主要转运蛋白介导了大部分的线粒体外膜分子运输。为了研究VDAC的天然超分子组织，我们从马铃薯块茎中分离、表征并对线粒体外膜进行了成像。线粒体外膜的SDS-PAGE和质谱分析显示存在VDAC亚型POM34和POM36，以及线粒体外膜复合物转位酶。将线粒体外膜在4℃孵育两到三个月后，VDAC自发形成管状二维晶体。透射电子显微镜显示出一个倾斜的晶格和包含六个呈六边形排列的圆形凹陷的晶胞。对新鲜分离的线粒体外膜进行原子力显微镜观察表明：（i）存在VDAC的单体至四聚体、六聚体及更高阶寡聚体；（ii）其在天然膜中寡聚体内的空间排列。我们讨论了观察到的寡聚化对于VDAC功能调节、己糖激酶和肌酸激酶与线粒体外膜结合以及线粒体介导的细胞凋亡的重要性。
