Santos Renata, Buisson Nicole, Knight Simon A B, Dancis Andrew, Camadro Jean-Michel, Lesuisse Emmanuel
Laboratoire d'Ingénierie des Protéines et Contrôle Métabolique, Département de Biologie des Génomes, Institut Jacques Monod, UMR 7592 CNRS-Universités Paris 6 and 7, 2 place Jussieu, F-75251 Paris cedex 05, France.
Mol Microbiol. 2004 Oct;54(2):507-19. doi: 10.1111/j.1365-2958.2004.04281.x.
We cloned the CaYFH1 gene that encodes the yeast frataxin homologue in Candida albicans. CaYFH1 was expressed in Deltayfh1 Saccharomyces cerevisiae cells, where it compensated for all the phenotypes tested except for the lack of cytochromes. Double DeltaCayfh1/DeltaCayfh1 mutant had severe defective growth, accumulated iron in their mitochondria, lacked aconitase and succinate dehydrogenase activity and had defective respiration. The reductive, siderophore and haem uptake systems were constitutively induced and the cells excreted flavins, thus behaving like iron-deprived wild-type cells. Mutant cells accumulated reactive oxygen species and were hypersensitive to oxidative stress, but not to iron. Cytochromes were less abundant in mutants than in wild-type cells, but this did not result from defective haem synthesis. The low cytochrome concentration in mutant cells was comparable to that of iron-deprived wild-type cells. Mitochondrial iron was still available for haem synthesis in DeltaCayfh1/DeltaCayfh1 cells, in contrast to S. cerevisaeDeltayfh1 cells. CaYFH1 transcription was strongly induced by iron, which is consistent with a role of CaYfh1 in iron storage. Iron also regulated transcription of CaHEM14 (encoding protoporphyrinogen oxidase) but not that of CaHEM15 (encoding ferrochelatase). There are thus profound differences between S. cerevisiae and C. albicans in terms of haem synthesis, cytochrome turnover and the role of frataxin in these processes.
我们克隆了白色念珠菌中编码酵母铁硫蛋白同源物的CaYFH1基因。CaYFH1在缺失YFH1的酿酒酵母细胞中表达，在该细胞中它补偿了除缺乏细胞色素外所测试的所有表型。双缺失CaYfh1/ΔCaYfh1突变体具有严重的生长缺陷，线粒体中铁积累，缺乏乌头酸酶和琥珀酸脱氢酶活性，呼吸功能有缺陷。还原、铁载体和血红素摄取系统被组成性诱导，细胞分泌黄素，因此表现得像缺铁的野生型细胞。突变细胞积累活性氧，对氧化应激敏感，但对铁不敏感。突变体中的细胞色素比野生型细胞中的少，但这不是由于血红素合成缺陷导致的。突变细胞中细胞色素浓度低与缺铁野生型细胞中的相当。与酿酒酵母缺失YFH1细胞不同，线粒体铁在双缺失CaYfh1/ΔCaYfh1细胞中仍可用于血红素合成。CaYFH1转录受铁强烈诱导，这与CaYfh1在铁储存中的作用一致。铁还调节CaHEM14（编码原卟啉原氧化酶）的转录，但不调节CaHEM15（编码亚铁螯合酶）的转录。因此，酿酒酵母和白色念珠菌在血红素合成、细胞色素周转以及铁硫蛋白在这些过程中的作用方面存在深刻差异。
