Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, Western Australia 6009, Australia.
Plant Physiol. 2011 Nov;157(3):1093-113. doi: 10.1104/pp.111.183160. Epub 2011 Sep 6.
The composition of the mitochondrial outer membrane is notoriously difficult to deduce by orthology to other organisms, and biochemical enrichments are inevitably contaminated with the closely associated inner mitochondrial membrane and endoplasmic reticulum. In order to identify novel proteins of the outer mitochondrial membrane in Arabidopsis (Arabidopsis thaliana), we integrated a quantitative mass spectrometry analysis of highly enriched and prefractionated samples with a number of confirmatory biochemical and cell biology approaches. This approach identified 42 proteins, 27 of which were novel, more than doubling the number of confirmed outer membrane proteins in plant mitochondria and suggesting novel functions for the plant outer mitochondrial membrane. The novel components identified included proteins that affected mitochondrial morphology and/or segregation, a protein that suggests the presence of bacterial type lipid A in the outer membrane, highly stress-inducible proteins, as well as proteins necessary for embryo development and several of unknown function. Additionally, proteins previously inferred via orthology to be present in other compartments, such as an NADH:cytochrome B5 reductase required for hydroxyl fatty acid accumulation in developing seeds, were shown to be located in the outer membrane. These results also revealed novel proteins, which may have evolved to fulfill plant-specific requirements of the mitochondrial outer membrane, and provide a basis for the future functional characterization of these proteins in the context of mitochondrial intracellular interaction.
线粒体外膜的组成成分很难通过与其他生物的同源性推断出来，生化富集不可避免地会受到密切相关的内线粒体膜和内质网的污染。为了鉴定拟南芥（Arabidopsis thaliana）中线粒体外膜的新蛋白，我们将高度富集和预分级样本的定量质谱分析与多种确证的生化和细胞生物学方法相结合。这种方法鉴定出了 42 种蛋白质，其中 27 种是新的，使植物线粒体中已确认的外膜蛋白数量增加了一倍以上，并暗示了植物外膜的新功能。鉴定出的新成分包括影响线粒体形态和/或分离的蛋白质、一种暗示外膜中存在细菌型脂 A 的蛋白质、高度应激诱导的蛋白质以及胚胎发育所必需的蛋白质和几种未知功能的蛋白质。此外，先前通过与其他隔室的同源性推断存在的蛋白质，例如在发育种子中积累羟基脂肪酸所需的 NADH：细胞色素 B5 还原酶，被证明位于外膜中。这些结果还揭示了新的蛋白质，它们可能是为了满足线粒体外膜的植物特异性要求而进化而来的，并为这些蛋白质在细胞器内相互作用的背景下进行未来的功能特征分析提供了基础。
