Skelton N J, Kördel J, Forsén S, Chazin W J
Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, CA 92037.
J Mol Biol. 1990 Jun 20;213(4):593-8. doi: 10.1016/s0022-2836(05)80244-x.
The solution structure of apo calbindin D9K, a member of the calmodulin superfamily of calcium-binding regulatory proteins, has been investigated by 1H nuclear magnetic resonance spectroscopy and the results compared with a corresponding study of the calcium-loaded protein. On the basis of complete sequence-specific assignments, characteristic patterns of short proton-proton distances have been identified in two-dimensional nuclear Overhauser effect spectra, allowing the elements of secondary structure to be determined. It is found that four helices and a short section of antiparallel beta-sheet are present regardless of the calcium content of the protein. In addition, a preliminary analysis of the long-range nuclear Overhauser effects shows that the global folding patterns are the same and that the tertiary structures of the apo protein is very similar to that of the calcium-loaded protein. These results are in stark contrast to a number of very substantial changes in 1H chemical shift. Preliminary studies of protein dynamics show some very large differences in flexibility and internal mobility. This suggests that protein dynamics may play a role more important than was initially realized in the function of calbindin D9K and other homologous calcium-binding regulatory proteins.
脱钙钙结合蛋白D9K是钙结合调节蛋白钙调蛋白超家族的成员之一，其溶液结构已通过1H核磁共振光谱进行了研究，并将结果与对钙负载蛋白的相应研究进行了比较。基于完整的序列特异性归属，在二维核Overhauser效应光谱中确定了短质子-质子距离的特征模式，从而能够确定二级结构元件。结果发现，无论蛋白质的钙含量如何，都存在四个螺旋和一小段反平行β折叠。此外，对长程核Overhauser效应的初步分析表明，整体折叠模式相同，脱钙蛋白的三级结构与钙负载蛋白的三级结构非常相似。这些结果与1H化学位移的一些非常显著的变化形成了鲜明对比。蛋白质动力学的初步研究表明，在灵活性和内部流动性方面存在一些非常大的差异。这表明，蛋白质动力学在钙结合蛋白D9K和其他同源钙结合调节蛋白的功能中可能发挥比最初意识到的更重要的作用。
