Kurokawa H, Mikami B, Hirose M
Research Institute for Food Science, Kyoto University, Japan.
J Mol Biol. 1995 Nov 24;254(2):196-207. doi: 10.1006/jmbi.1995.0611.
The three-dimensional structure of diferric hen ovotransferrin has been determined by X-ray crystallography at 2.4 A resolution. The structure was solved by molecular replacement, using the coordinates of diferric human lactoferrin as a search model. Several rounds of simulated annealing and restrained least-squares refinement have resulted in a model structure with an R-factor of 0.171 for the data between 11.0 and 2.4 A resolution. The model comprises 5284 protein atoms (residues 5 to 686), 2 Fe3+, 2 CO3(2)- and 132 water molecules. The overall structure of ovotransferrin is similar to those of human lactoferrin and rabbit serum transferrin, being folded into two homologous lobes, each containing two dissimilar domains with one Fe3+ and one CO3(2)- bound at a specific site in each interdomain cleft. However, the relative orientation of the two lobes, which may be related to the class specificity of transferrins to receptors, is different from either human lactoferrin or rabbit serum transferrin. The angle of the relative orientation in ovotransferrin is increased by 6.8 degrees and 15.7 degrees as compared with to those in rabbit serum transferrin and human lactoferrin, respectively. Interdomain Lys209-Lys301 and Gln541-Lys638 interactions are found near the metal binding site of each lobe. The interlobe interactions and their role in the stabilization of iron binding are discussed.
通过X射线晶体学在2.4埃分辨率下测定了二价铁鸡卵转铁蛋白的三维结构。该结构通过分子置换法解析，使用二价铁人乳铁蛋白的坐标作为搜索模型。经过几轮模拟退火和约束最小二乘精修，得到了一个模型结构，对于11.0至2.4埃分辨率的数据，其R因子为0.171。该模型包含5284个蛋白质原子（残基5至686）、2个Fe3+、2个CO3(2)-和132个水分子。卵转铁蛋白的整体结构与人类乳铁蛋白和兔血清转铁蛋白相似，折叠成两个同源结构域，每个结构域包含两个不同的亚结构域，每个亚结构域间裂隙的特定位点结合有一个Fe3+和一个CO3(2)-。然而，两个结构域的相对取向可能与转铁蛋白对受体的类别特异性有关，与人类乳铁蛋白或兔血清转铁蛋白不同。与兔血清转铁蛋白和人类乳铁蛋白相比，卵转铁蛋白中相对取向的角度分别增加了6.8度和15.7度。在每个结构域的金属结合位点附近发现了结构域间的Lys209-Lys301和Gln541-Lys638相互作用。讨论了结构域间相互作用及其在铁结合稳定中的作用。
