Juszczuk Izabela M, Rychter Anna M
Institute of Experimental Plant Biology, University of Warsaw, Poland.
Plant Physiol Biochem. 2009 May;47(5):397-406. doi: 10.1016/j.plaphy.2008.12.022. Epub 2009 Jan 9.
Rearrangements of mitochondrial DNA in MSC16 mutant of cucumber (Cucumis sativus L.) affect mitochondrial functioning due to the alteration mainly of Complex I resulting in several metabolic changes. One-dimensional Blue-Native polyacrylamide gel electrophoresis (BN-PAGE) and densitometric measurements showed that the level and in-gel capacity of Complex I were lower in MSC16 leaf and root mitochondria as compared to wild-type (WT). The level and capacity of supercomplex I+III(2) were always lower in leaf but not in MSC16 root mitochondria. Two-dimensional BN/SDS-PAGE indicated that the band abundance for most of the subunits of Complex I was lower in MSC16 leaf and root mitochondria. Supercomplex I+III(2) level was only altered in MSC16 leaf mitochondria as measured after 2D BN/SDS-PAGE. No differences in the qualitative composition of the subunits of Complex I and supercomplex I+III(2) between MSC16 and WT mitochondria were observed. In MSC16 mitochondria Complex I impairment could be compensated to some extent by additional respiratory chain NADH dehydrogenases. A higher capacity and level of NDB-1 protein of external NADH dehydrogenase was observed in MSC16 leaf and root mitochondria as compared to WT. The level of COX II, mitochondrial-encoded subunit of Complex IV, was higher in MSC16 leaf and root mitochondria. However, the capacity of Complex IV was slightly higher only in MSC16 leaf mitochondria. The levels of complexes: III(2) and V and Complex V capacity did not differ in mitochondria between genotypes. An abundance of the subunits of respiratory complexes is one of the key factors determining not only their structure and functional stability but also a formation of the supercomplexes. We discuss here mitochondrial genome rearrangements in MSC16 mutant in a relation to assembly and/or stability (the lower level and capacity) of Complex I and supercomplex I+III(2).
黄瓜（Cucumis sativus L.）MSC16突变体中线粒体DNA的重排会影响线粒体功能，这主要是由于复合体I的改变导致了多种代谢变化。一维蓝色天然聚丙烯酰胺凝胶电泳（BN-PAGE）和光密度测量结果表明，与野生型（WT）相比，MSC16叶片和根线粒体中复合体I的水平和凝胶内活性较低。超复合体I+III(2)的水平和活性在叶片中始终较低，但在MSC16根线粒体中并非如此。二维BN/SDS-PAGE表明，MSC16叶片和根线粒体中复合体I大多数亚基的条带丰度较低。二维BN/SDS-PAGE检测后发现，超复合体I+III(2)水平仅在MSC16叶片线粒体中发生改变。未观察到MSC16和WT线粒体中复合体I及超复合体I+III(2)亚基的定性组成存在差异。在MSC16线粒体中，复合体I的损伤可通过额外的呼吸链NADH脱氢酶得到一定程度的补偿。与WT相比，在MSC16叶片和根线粒体中观察到外部NADH脱氢酶NDB-1蛋白的活性和水平更高。复合体IV的线粒体编码亚基COX II在MSC16叶片和根线粒体中的水平较高。然而，仅在MSC16叶片线粒体中复合体IV的活性略高。复合体III(2)和V以及复合体V活性在不同基因型的线粒体中没有差异。呼吸复合体亚基的丰度不仅是决定其结构和功能稳定性的关键因素之一，也是决定超复合体形成的关键因素之一。我们在此讨论MSC16突变体中线粒体基因组重排与复合体I和超复合体I+III(2)的组装和/或稳定性（较低的水平和活性）之间的关系。
