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首页> 外文期刊>Journal of Molecular Biology >THREE-DIMENSIONAL STRUCTURE OF DIFERRIC BOVINE LACTOFERRIN AT 2.8 ANGSTROM RESOLUTION
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THREE-DIMENSIONAL STRUCTURE OF DIFERRIC BOVINE LACTOFERRIN AT 2.8 ANGSTROM RESOLUTION

机译：2.8埃分辨力的牛乳乳铁蛋白的三维结构

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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. [References: 63]
机译：为了研究影响铁结合和转铁蛋白释放的因素，已通过X射线晶体学确定了二铁牛乳铁蛋白（bLf）的三维结构。该结构通过分子置换来解决，使用二铁人乳铁蛋白（hLf）的坐标作为搜索模型，并通过模拟退火（X-PLOR）和约束最小二乘（TNT）将数据精炼为2.8埃分辨率。最终模型包含5310个蛋白质原子（5至689位残基），124个碳水化合物原子（来自三个聚糖链中的10个单糖单元），2Fe（3 +），2CO（3）（2-）和50个水分子。对于31440至2.8埃分辨率范围内的21440次反射，该模型的R因子为0.232。 bLf分子的折叠与hLf的折叠基本相同，但是bLf的区别在于每个叶的两个结构域的闭合程度不同。并沿两个瓣的相对方向排列。域关闭的差异归因于界面中的氨基酸变化，而叶方向的差异归因于叶之间两个疏水性补丁的填充略有改变。域间相互作用的变化可能解释了与hLf相比，bLf的铁亲和力较小，并且bLf的N裂片铁位点后面的两个赖氨酸残基为“转铁蛋白释放铁”的“二赖氨酸触发”机制提供了新见解。 bLf结构在几个明确定义的寡糖单元中也很明显，这些单元显示出稳定碳水化合物结构的结构因子。连接到Asn545的一条聚糖链似乎有助于域间相互作用，并可能调节铁从C瓣的释放。 （C）1997 Academic Press Limited。 [参考：63]

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