Gérin Stéphanie, Mathy Grégory, Blomme Arnaud, Franck Fabrice, Sluse Francis E
Laboratory of bioenergetics and cellular physiology, B6, Allée de la Chimie 3, 4000 Liège, Belgium.
Biochim Biophys Acta. 2010 Jun-Jul;1797(6-7):994-1003. doi: 10.1016/j.bbabio.2010.02.034. Epub 2010 Mar 6.
Nitrate and ammonium constitute primary inorganic nitrogen sources that can be incorporated into carbon skeletons in photosynthetic eukaryotes. In Chlamydomonas, previous studies and the present one showed that the mitochondrial AOX is up-regulated in nitrate-grown cells in comparison with ammonium-grown cells. In this work, we have performed a comparative proteomic analysis of the soluble mitochondrial proteome of Chlamydomonas cells growth either on nitrate or ammonium. Our results highlight important proteomics modifications mostly related to primary metabolism in cells grown on nitrate. We could note an up-regulation of some TCA cycle enzymes and a down-regulation of cytochrome c1 together with an up-regulation of l-arginine and purine catabolism enzymes and of ROS scavenging systems. Hence, in nitrate-grown cells, AOX may play a dual role: (1) lowering the ubiquinone pool reduction level and (2) permitting the export of mitochondrial reducing power under the form of malate for nitrate and nitrite reduction. This role of AOX in the mitochondrial plasticity makes logical the localization of Aox1 in a nitrate assimilation gene cluster.
硝酸盐和铵构成了主要的无机氮源，可被光合真核生物纳入碳骨架中。在衣藻中，先前的研究以及本研究均表明，与铵培养的细胞相比，线粒体AOX在硝酸盐培养的细胞中上调。在这项工作中，我们对衣藻细胞在硝酸盐或铵上生长时的可溶性线粒体蛋白质组进行了比较蛋白质组学分析。我们的结果突出了重要的蛋白质组学修饰，这些修饰大多与硝酸盐培养的细胞中的初级代谢有关。我们可以注意到一些三羧酸循环酶的上调、细胞色素c1的下调，以及L-精氨酸和嘌呤分解代谢酶和活性氧清除系统的上调。因此，在硝酸盐培养的细胞中，AOX可能发挥双重作用：（1）降低泛醌池的还原水平；（2）以苹果酸的形式允许线粒体还原力输出，用于硝酸盐和亚硝酸盐的还原。AOX在这种线粒体可塑性中的作用使得Aox1定位于硝酸盐同化基因簇中变得合乎逻辑。
