Role of H-1 and H-2 Subunits of Soybean Seed Ferritin in Oxidative Deposition of Iron in Protein
Role of H-1 and H-2 Subunits of Soybean Seed Ferritin in Oxidative Deposition of Iron in Protein
复制标题
大豆种子铁蛋白H-1和H-2亚基在蛋白质中铁氧化沉积中的作用
DOI：
10.1074/jbc.m110.130435
复制
发表时间：
2010-10-15
影响因子：
4.8
通讯作者：
Zhao, Guanghua
中科院分区：
文献类型：
--
作者：
Deng, Jianjun;Liao, Xiayun;Zhao, Guanghua
天然存在的植物铁蛋白是由两个不同的 H 型亚基 H-1 和 H-2 组成的杂聚物。然而，在这项研究之前，这两个亚基在铁蛋白中铁氧化沉积中的功能尚不清楚。数据显示，在有氧添加 48-200 Fe2+/壳至脱铁铁蛋白时，铁氧化仅发生在重组 H1 (rH-1) 的二铁亚铁氧化酶中心。除了二铁亚铁氧化酶机制之外，这种氧化还受到rH-2的延伸肽（植物铁蛋白中发现的特定结构域）的催化，因为H-1亚基能够比H-2亚基更好地将Fe3+从中心去除到内腔。这些发现支持 H-1 和 H-2 亚基在蛋白质铁矿化中发挥不同作用的观点。有趣的是，在中等铁负载量（200个铁/壳）下，野生型（WT）大豆种子铁蛋白（SSF）在催化铁氧化方面表现出比rH-1（0.59+/-0.07μM铁/亚基/秒）和rH-2（0.48+/-0.04μM铁/亚基/秒）更强的催化铁氧化活性（1.10+/-0.13μM铁/亚基/秒）。铁/亚基/s），证明在铁矿化过程中，SSF 中的 H-1 和 H-2 亚基之间存在协同相互作用。 WT SSF 的铁氧化活性比 rH-1 和 rH-2 的铁氧化活性大 10 倍，这表明这种协同相互作用在高铁负载量（400 个铁/壳）下变得相当强。这有助于阐明杂聚铁蛋白在植物中的广泛存在。
Naturally occurring phytoferritin is a heteropolymer consisting of two different H-type subunits, H-1 and H-2. Prior to this study, however, the function of the two subunits in oxidative deposition of iron in ferritin was unknown. The data show that, upon aerobic addition of 48-200 Fe2+/shell to apoferritin, iron oxidation occurs only at the diiron ferroxidase center of recombinant H1 (rH-1). In addition to the diiron ferroxidase mechanism, such oxidation is catalyzed by the extension peptide (a specific domain found in phytoferritin) of rH-2, because the H-1 subunit is able to remove Fe3+ from the center to the inner cavity better than the H-2 subunit. These findings support the idea that the H-1 and H-2 subunits play different roles in iron mineralization in protein. Interestingly, at medium iron loading (200 irons/shell), wild-type (WT) soybean seed ferritin (SSF) exhibits a stronger activity in catalyzing iron oxidation (1.10 +/- 0.13 mu M iron/subunit/s) than rH-1 (0.59 +/- 0.07 mu M iron/subunit/s) and rH-2 (0.48 +/- 0.04 mu M iron/subunit/s), demonstrating that a synergistic interaction exists between the H-1 and H-2 subunits in SSF during iron mineralization. Such synergistic interaction becomes considerably stronger at high iron loading (400 irons/shell) as indicated by the observation that the iron oxidation activity of WT SSF is similar to 10 times larger than those of rH-1 and rH-2. This helps elucidate the widespread occurrence of heteropolymeric ferritins in plants.