Lobreaux S, Yewdall S J, Briat J F, Harrison P M
Laboratoire de Biologie Moléculaire Végétale, Centre National de la Recherche Scientifique (Unité de Recherche Associée 1178) Grenoble, France.
Biochem J. 1992 Dec 15;288 ( Pt 3)(Pt 3):931-9. doi: 10.1042/bj2880931.
The iron storage protein, ferritin, is widely distributed in the living kingdom. Here the complete cDNA and derived amino-acid sequence of pea seed ferritin are described, together with its predicted secondary structure, namely a four-helix-bundle fold similar to those of mammalian ferritins, with a fifth short helix at the C-terminus. An N-terminal extension of 71 residues contains a transit peptide (first 47 residues) responsible for plastid targetting as in other plant ferritins, and this is cleaved before assembly. The second part of the extension (24 residues) belongs to the mature subunit; it is cleaved during germination. The amino-acid sequence of pea seed ferritin is aligned with those of other ferritins (49% amino-acid identity with H-chains and 40% with L-chains of human liver ferritin in the aligned region). A three-dimensional model has been constructed by fitting the aligned sequence to the coordinates of human H-chains, with appropriate modifications. A folded conformation with an 11-residue helix is predicted for the N-terminal extension. As in mammalian ferritins, 24 subunits assemble into a hollow shell. In pea seed ferritin, its N-terminal extension is exposed on the outside surface of the shell. Within each pea subunit is a ferroxidase centre resembling those of human ferritin H-chains except for a replacement of Glu-62 by His. The channel at the 4-fold-symmetry axes defined by E-helices, is predicted to be hydrophilic in plant ferritins, whereas it is hydrophobic in mammalian ferritins.
铁储存蛋白——铁蛋白，广泛分布于生物界。本文描述了豌豆种子铁蛋白完整的cDNA及其推导的氨基酸序列，以及其预测的二级结构，即与哺乳动物铁蛋白类似的四螺旋束折叠结构，在C端有第五个短螺旋。71个残基的N端延伸部分包含一个转运肽（前47个残基），与其他植物铁蛋白一样，负责向质体靶向运输，并且在组装前被切割。延伸部分的第二部分（24个残基）属于成熟亚基；它在萌发过程中被切割。豌豆种子铁蛋白的氨基酸序列与其他铁蛋白的序列进行了比对（在比对区域与人类肝脏铁蛋白的H链有49%的氨基酸同一性，与L链有40%的氨基酸同一性）。通过将比对后的序列与人类H链的坐标进行拟合，并进行适当修改，构建了一个三维模型。预测N端延伸部分具有一个11个残基的螺旋的折叠构象。与哺乳动物铁蛋白一样，24个亚基组装成一个空心壳。在豌豆种子铁蛋白中，其N端延伸部分暴露在壳的外表面。在每个豌豆亚基内有一个亚铁氧化酶中心，除了将人类铁蛋白H链中的Glu-62替换为His外，与人类铁蛋白H链的亚铁氧化酶中心相似。由E螺旋定义的四重对称轴处的通道，预计在植物铁蛋白中是亲水的，而在哺乳动物铁蛋白中是疏水的。
