Nature：硅藻中发现铁蛋白

专题：Nature报道 非血红素蛋白“铁蛋白”被很多植物、动物和微生物用来以一种非毒性可溶形式存储铁，这种形式在需要时容易被利用。 美国和加拿大的研究人员最近在两种硅藻中发现了，“铁蛋白”。它们分别是Pseudo-nitzschia 和 Fragilariopsis。这两种硅藻主导由以自然方式和人工方式为海洋中补充铁所诱导的浮游植物繁盛现象。这是在“金黄藻菌鞭毛菌界”（Stramenopila）任何一个成员中关于“铁蛋白”的首次报告。 “金黄藻菌鞭毛菌界”是真核生物的一个分支，包括很多浮游植物，如单细胞藻类、硅藻和大型藻类等。




蛋白质结合铁原子示意图，图中粉色为铁原子
系统发育分析表明，“铁蛋白”是通过侧向基因转移在硅藻的这一小类别中出现的，它也许是它们在铁供应为初级生产力限制因素的30-40%的海洋中能够成功生存的关键。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 457, 467-470 (22 January 2009) doi:10.1038/nature07539
Ferritin is used for iron storage in bloom-forming marine pennate diatoms
Adrian Marchetti1,4, Micaela S. Parker1,4, Lauren P. Moccia2, Ellen O. Lin1, Angele L. Arrieta3, Francois Ribalet1, Michael E. P. Murphy3, Maria T. Maldonado2 & E. Virginia Armbrust1
1 School of Oceanography, University of Washington, Box 357940, Seattle, Washington 98195, USA 2 Department of Earth and Ocean Sciences, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia V6T 1Z4, Canada 3 Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada 4 These authors contributed equally to this work.
Primary productivity in 30–40% of the world's oceans is limited by availability of the micronutrient iron1, 2. Regions with chronically low iron concentrations are sporadically pulsed with new iron inputs by way of dust3 or lateral advection from continental margins4. Addition of iron to surface waters in these areas induces massive phytoplankton blooms dominated primarily by pennate diatoms5, 6. Here we provide evidence that the bloom-forming pennate diatoms Pseudo-nitzschia and Fragilariopsis use the iron-concentrating protein, ferritin, to safely store iron. Ferritin has not been reported previously in any member of the Stramenopiles, a diverse eukaryotic lineage that includes unicellular algae, macroalgae and plant parasites. Phylogenetic analyses suggest that ferritin may have arisen in this small subset of diatoms through a lateral gene transfer. The crystal structure and functional assays of recombinant ferritin derived from Pseudo-nitzschia multiseries reveal a maxi-ferritin that exhibits ferroxidase activity and binds iron. The protein is predicted to be targeted to the chloroplast to control the distribution and storage of iron for proper functioning of the photosynthetic machinery. Abundance of Pseudo-nitzschia ferritin transcripts is regulated by iron nutritional status, and is closely tied to the loss and recovery of photosynthetic competence. Enhanced iron storage with ferritin allows the oceanic diatom Pseudo-nitzschia granii to undergo several more cell divisions in the absence of iron than the comparably sized, oceanic centric diatom Thalassiosira oceanica. Ferritin in pennate diatoms probably contributes to their success in chronically low-iron regions that receive intermittent iron inputs, and provides an explanation for the importance of these organisms in regulating oceanic CO2 over geological timescales7, 8.