Dörner M H, Salfeld J, Will H, Leibold E A, Vass J K, Munro H N
Proc Natl Acad Sci U S A. 1985 May;82(10):3139-43. doi: 10.1073/pnas.82.10.3139.
Ferritin has a protein shell of 5 X 10(6) Da consisting of 24 subunits of two types, a heavier (H) chain of 21,000 Da and a lighter (L) chain of 19,000 Da. A cDNA clone of the messenger for the L subunit has been isolated from a human monocyte-like leukemia cell line. The clone contains an open reading frame of 522 nucleotides coding for an amino acid sequence matching 97% of the published sequence of human liver ferritin L subunit determined by sequenator, but it corresponds to only 55% of the reported amino acid sequence of a human liver H-subunit clone. Nevertheless, computer analysis of the subunit conformations predicted from the open reading frames of the L and H clones shows that most of the amino acid differences are conservative and would allow both subunits to form the five alpha-helices and beta-turns established by x-ray crystallography for horse spleen ferritin subunits. This suggests that L and H subunits are structurally interchangeable in forming an apoferritin shell. The 5' untranslated region of our human ferritin L clone has considerable homology with that of the rat liver ferritin L clone in the region immediately upstream from the initiator codon, notably showing an identical sequence of 10 nucleotides at the same position in both subunit clones that may participate in regulating the known activation of ferritin mRNA after iron administration. Extensive homology, including several blocks of nucleotides, was identified between the 3' untranslated regions of the human and rat L clones. The common structural features of the H and L subunits lead us to conclude that they have diverged from a single ancestral gene.
铁蛋白有一个5×10⁶道尔顿的蛋白质外壳，由两种类型的24个亚基组成，一种是较重的（H）链，分子量为21,000道尔顿，另一种是较轻的（L）链，分子量为19,000道尔顿。已从人单核细胞样白血病细胞系中分离出L亚基信使核糖核酸的一个互补脱氧核糖核酸（cDNA）克隆。该克隆含有一个522个核苷酸的开放阅读框，编码的氨基酸序列与通过序列分析仪测定的人肝铁蛋白L亚基已发表序列的97%相匹配，但它仅对应于人肝H亚基克隆报道的氨基酸序列的55%。然而，对从L和H克隆的开放阅读框预测的亚基构象进行计算机分析表明，大多数氨基酸差异是保守的，并且会使两个亚基都能形成由马脾铁蛋白亚基的X射线晶体学确定的五个α螺旋和β转角。这表明L和H亚基在形成脱铁铁蛋白外壳时在结构上是可互换的。我们的人铁蛋白L克隆的5'非翻译区与大鼠肝铁蛋白L克隆的5'非翻译区在起始密码子上游紧邻区域有相当的同源性，特别是在两个亚基克隆的相同位置显示出10个核苷酸的相同序列，这可能参与调节铁给药后已知的铁蛋白信使核糖核酸的激活。在人和大鼠L克隆的3'非翻译区之间鉴定出广泛的同源性，包括几个核苷酸块。H和L亚基的共同结构特征使我们得出结论，它们是从一个单一的祖先基因分化而来的。
