Three-dimensional structure of diferric bovine lactoferrin at 2.8 angstrom resolution
Three-dimensional structure of diferric bovine lactoferrin at 2.8 angstrom resolution
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DOI：
10.1006/jmbi.1997.1386
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发表时间：
1997-11-28
影响因子：
5.6
通讯作者：
Baker, EN
中科院分区：
文献类型：
--
作者：
Moore, SA;Anderson, BF;Baker, EN
用X射线晶体学方法测定了牛乳铁蛋白（bLf）的三维结构，以探讨影响转铁蛋白结合和释放铁的因素。使用二铁人乳铁蛋白（hLf）的坐标作为搜索模型，通过分子置换来解析结构，并通过模拟退火（X-PLOR）和约束最小二乘法（TNT）用数据将其细化到2.8埃分辨率。最终模型包含5310个蛋白质原子（残基5至689），124个碳水化合物原子（来自三个聚糖链中的十个单糖单元），2Fe（3+），2CO（3）（2-）和50个水分子。该模型在30.0至2.8埃的分辨率范围内对21440次反射给出了0.232的R因子。bLf分子的折叠基本上与hLf相同，但bLf在每个叶的两个结构域的闭合程度以及两个叶的相对取向上不同。域关闭的差异是由于氨基酸的变化，在界面上，并在叶方向略有改变的两个疏水补丁之间的叶包装的差异。改变域间的相互作用可以解释较低的铁亲和力的bLf，与hLf相比，和两个赖氨酸残基后面的N-叶铁网站的bLf提供了新的见解的“二赖氨酸酶”机制提出的铁释放转铁蛋白。bLf结构也值得注意的是几个明确定义的寡糖单元，这些单元证明了稳定碳水化合物结构的结构因素。一个聚糖链，连接到Asn 545，似乎有助于域间的相互作用，并可能调节铁从C叶释放。(C)出版社：Academic Press Limited。
The three-dimensional structure of diferric bovine lactoferrin (bLf) has been determined by X-ray crystallography in order to investigate the factors that influence iron binding and release by transferrins. The structure was solved by molecular replacement, using the coordinates of diferric human lactoferrin (hLf) as a search model, and was refined with data to 2.8 Angstrom resolution by simulated annealing (X-PLOR) and restrained least squares (TNT). The final model comprises 5310 protein atoms (residues 5 to 689), 124 carbohydrate atoms (from ten monosaccharide units, in three glycan chains), 2Fe(3+), 2CO(3)(2-) and 50 water molecules. This model gives an R-factor of 0.232 for 21440 reflections in the resolution range 30.0 to 2.8 Angstrom. The folding of the bLf molecule is essentially the same as that of hLf, but bLf differs in the extent of closure of the two domains of each lobe; and in the relative orientations of the two lobes. Differences in domain closure are attributed to amino acid changes in the interface, and differences in lobe orientations to slightly altered packing of two hydrophobic patches between the lobes. Changed interdomain interactions may explain the lesser iron affinity of bLf, compared with hLf, and two lysine residues behind the N-lobe iron site of bLf offer new insights into the ''dilysine trigger'' mechanism proposed for iron release by transferrins. The bLf structure is also notable for several well-defined oligosaccharide units which demonstrate the structural factors that stabilise carbohydrate structure. One glycan chain, attached to Asn545, appears to contribute to interdomain interactions and may modulate iron release from the C-lobe. (C) 1997 Academic Press Limited.