Lezhneva Lina, Amann Katrin, Meurer Jörg
Ludwig-Maximilians-Universität, Department Biologie I, Botanik, Menzingerstr 67, 80638 Munich, Germany.
Plant J. 2004 Jan;37(2):174-85. doi: 10.1046/j.1365-313x.2003.01952.x.
The seedling-lethal nuclear Arabidopsis hcf101 (high chlorophyll fluorescence) mutant is impaired in photosynthesis and complemented by the wild-type HCF101 cDNA. Photosystem I (PSI) activity is abolished, and PSI core complexes fail to accumulate in hcf101, whereas levels of other thylakoid membrane proteins are unaffected. Northern and in vivo labelling analyses as well as studies on polysome loading show that PSI transcript levels and translation rates of proteins, which belong to PSI, are normal in hcf101. PSI-specific fluorescence at 77 K is shifted from 735 to 728 nm in hcf101, indicating that exitons cannot efficiently be transferred to the PSI reaction centre, whereby the PSI antenna is almost unaffected. Mutant plants not only fail to accumulate mature PSI, which contains three [4Fe-4S]clusters (FSCs), but also are characterized by reduced levels of the soluble FSC-containing complex ferredoxin-thioredoxin reductase (FTR) in the stroma. Inhibited FTR maturation is not a secondary effect stemming from lack of PSI because the mutant hcf145, which also lacks PSI, accumulates FTR at normal levels. Levels of the [2Fe-2S] cluster-containing soluble and membrane proteins, ferredoxin and PetC, respectively, were unchanged in hcf101 plants. These data suggest a specific role of HCF101 in FSC biogenesis. HCF101 is plastid localized and belongs to an ancient and universally conserved family of P-loop ATPases previously designated as the 'MRP' (metGrelated protein) family. The function identified for HCF101 suggests a new designation, FSC, for this family.
幼苗致死型拟南芥hcf101（高叶绿素荧光）突变体在光合作用方面存在缺陷，可被野生型HCF101 cDNA互补。光系统I（PSI）活性丧失，并且PSI核心复合物在hcf101中无法积累，而其他类囊体膜蛋白的水平不受影响。Northern印迹和体内标记分析以及多核糖体负载研究表明，在hcf101中，PSI转录本水平和属于PSI的蛋白质的翻译速率是正常的。在hcf101中，77 K时PSI特异性荧光从735 nm移至728 nm，这表明激子不能有效地转移到PSI反应中心，由此PSI天线几乎不受影响。突变植株不仅无法积累含有三个[4Fe-4S]簇（FSCs）的成熟PSI，而且其基质中含可溶性FSC的复合物铁氧还蛋白-硫氧还蛋白还原酶（FTR）水平降低。FTR成熟受抑制并非由于缺乏PSI产生的次级效应，因为同样缺乏PSI的突变体hcf145能正常积累FTR。在hcf101植株中，分别含有[2Fe-2S]簇的可溶性蛋白铁氧还蛋白和膜蛋白PetC的水平没有变化。这些数据表明HCF101在FSC生物合成中具有特定作用。HCF101定位于质体，属于一个古老且普遍保守的P环ATP酶家族，该家族先前被命名为“MRP”（与metG相关的蛋白）家族。为HCF101确定的功能为此家族提出了一个新名称——FSC。
