Protein Association and Dissociation Regulated by Ferric Ion A NOVEL PATHWAY FOR OXIDATIVE DEPOSITION OF IRON IN PEA SEED FERRITIN
Protein Association and Dissociation Regulated by Ferric Ion A NOVEL PATHWAY FOR OXIDATIVE DEPOSITION OF IRON IN PEA SEED FERRITIN
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DOI：
10.1074/jbc.m109.011528
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发表时间：
2009-06-19
影响因子：
4.8
通讯作者：
Zhao, Guanghua
中科院分区：
文献类型：
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作者：
Li, Chaorui;Fu, Xiaoping;Zhao, Guanghua
植物铁蛋白中储存的铁在幼苗萌发和早期生长中起着重要作用。这种蛋白质位于淀粉体中，在其壳状结构中以水合氧化铁矿物核的形式储存了大量的铁。本文研究了豌豆种子铁蛋白（PSF）核形成的其他机制。这些数据揭示了PSF中矿物核形成的新机制，涉及位于蛋白外壳外表面的延伸肽（EP）的铁的结合和氧化。这种结合诱导蛋白质聚集成类似400个单体的大组装体。结合的铁逐渐转移到矿物核心，在此期间，蛋白质解离回其单体状态。一旦超过24个铁氧化酶中心（48个Fe3+ /壳）的结合能力，要么将Fe2+氧化加入载脂蛋白形成Fe3+，要么将Fe3+直接加入载脂蛋白sf，都会导致蛋白质聚集。当EP从PSF中被酶删除时，没有观察到聚集，铁的氧化速率显著降低，表明EP是铁结合、氧化和蛋白质聚集的关键结构成分。这些数据表明延伸肽作为铁结合和铁氧化酶中心的功能作用有助于铁核的矿化。随着铁核的增大，新的途径变得不那么重要，Fe2+的氧化和沉积直接发生在铁核表面。
Iron stored in phytoferritin plays an important role in the germination and early growth of seedlings. The protein is located in the amyloplast where it stores large amounts of iron as a hydrated ferric oxide mineral core within its shell-like structure. The present work was undertaken to study alternate mechanisms of core formation in pea seed ferritin (PSF). The data reveal a new mechanism for mineral core formation in PSF involving the binding and oxidation of iron at the extension peptide (EP) located on the outer surface of the protein shell. This binding induces aggregation of the protein into large assemblies of similar to 400 monomers. The bound iron is gradually translocated to the mineral core during which time the protein dissociates back into its monomeric state. Either the oxidative addition of Fe2+ to the apoprotein to form Fe3+ or the direct addition of Fe3+ to apoPSF causes protein aggregation once the binding capacity of the 24 ferroxidase centers (48 Fe3+ / shell) is exceeded. When the EP is enzymatically deleted from PSF, aggregation is not observed, and the rate of iron oxidation is significantly reduced, demonstrating that the EP is a critical structural component for iron binding, oxidation, and protein aggregation. These data point to a functional role for the extension peptide as an iron binding and ferroxidase center that contributes to mineralization of the iron core. As the iron core grows larger, the new pathway becomes less important, and Fe2+ oxidation and deposition occurs directly on the surface of the iron core.