The extension peptide of plant ferritin from sea lettuce contributes to shell stability and surface hydrophobicity
The extension peptide of plant ferritin from sea lettuce contributes to shell stability and surface hydrophobicity
复制标题
DOI：
10.1002/pro.2061
复制
发表时间：
2012-06-01
期刊：
影响因子：
8
通讯作者：
Toyohara, Haruhiko
中科院分区：
文献类型：
--
作者：
Masuda, Taro;Morimoto, Shin-Ichiro;Toyohara, Haruhiko
植物铁蛋白具有一些独特的结构和功能特征。大多数这些特征可能与植物特异性延伸肽 (EP) 有关，该肽存在于植物铁蛋白成熟区域的 N 末端。最近对植物铁蛋白的晶体学分析揭示了 EP 的结构，然而，有两点仍不清楚：(i) 植物铁蛋白保守的 EP 结构是否在所有植物中常见，以及 (ii) EP 是否真正有助于植物铁蛋白低聚物的壳稳定性。为了澄清这些问题，我们从绿藻 Ulva pertusa 中克隆了绿色植物型铁蛋白 cDNA，并研究了其晶体结构。石莼铁蛋白 (UpFER) 具有由 28 个氨基酸残基组成的植物铁蛋白特异性延伸肽。在 UpFER 的晶体结构中，EP 位于邻近的三重对称相关亚基上并与其相互作用。参与相互作用的氨基酸残基在植物铁蛋白中高度保守。 EP 通过位于铁蛋白壳表面的疏水袋上来掩盖它们，这使得铁蛋白低聚物更加亲水。此外，对天然铁蛋白及其 EP 缺失突变体的差示扫描量热分析表明，EP 有助于植物铁蛋白壳的热稳定性。因此，植物铁蛋白的壳稳定性和表面疏水性是由植物铁蛋白特异性 EP 的存在或不存在来控制的。这种调节可以解释植物铁蛋白的壳稳定性、降解和缔合等过程，这些过程与植物中的铁利用显着相关。
Plant ferritins have some unique structural and functional features. Most of these features can be related to the plant-specific extension peptide (EP), which exists in the N-terminus of the mature region of a plant ferritin. Recent crystallographic analysis of a plant ferritin revealed the structure of the EP, however, two points remain unclear: (i) whether the structures of well-conserved EP of plant ferritins are common in all plants, and (ii) whether the EP truly contributes to the shell stability of the plant ferritin oligomer. To clarify these matters, we have cloned a green-plant-type ferritin cDNA from a green alga, Ulva pertusa, and investigated its crystal structure. Ulva pertusa ferritin (UpFER) has a plant-ferritin-specific extension peptide composed of 28 amino acid residues. In the crystal structure of UpFER, the EP lay on and interacted with the neighboring threefold symmetry-related subunit. The amino acid residues involved in the interaction were very highly conserved among plant ferritins. The EPs masked the hydrophobic pockets on the ferritin shell surface by lying on them, and this made the ferritin oligomer more hydrophilic. Furthermore, differential scanning calorimetric analysis of the native and its EP-deletion mutant suggested that the EP contributed to the thermal stability of the plant ferritin shell. Thus, the shell stability and surface hydrophobicity of plant ferritin were controlled by the presence or absence of the plant-ferritin-specific EP. This regulation can account for those processes such as shell stability, degradation, and association of plant ferritin, which are significantly related to iron utilization in plants.