Carlon Azzurra, Ravera Enrico, Andrałojć Witold, Parigi Giacomo, Murshudov Garib N, Luchinat Claudio
Magnetic Resonance Center (CERM) and Department of Chemistry "Ugo Schiff", University of Florence, Italy(1).
MRC Laboratory for Molecular Biology, Francis Crick Ave, Cambridge CB2 0QH, UK.
Prog Nucl Magn Reson Spectrosc. 2016 Feb;92-93:54-70. doi: 10.1016/j.pnmrs.2016.01.001. Epub 2016 Jan 21.
Long-range NMR restraints, such as diamagnetic residual dipolar couplings and paramagnetic data, can be used to determine 3D structures of macromolecules. They are also used to monitor, and potentially to improve, the accuracy of a macromolecular structure in solution by validating or "correcting" a crystal model. Since crystal structures suffer from crystal packing forces they may not be accurate models for the macromolecular structures in solution. However, the presence of real differences should be tested for by simultaneous refinement of the structure using both crystal and solution NMR data. To achieve this, the program REFMAC5 from CCP4 was modified to allow the simultaneous use of X-ray crystallographic and paramagnetic NMR data and/or diamagnetic residual dipolar couplings. Inconsistencies between crystal structures and solution NMR data, if any, may be due either to structural rearrangements occurring on passing from the solution to solid state, or to a greater degree of conformational heterogeneity in solution with respect to the crystal. In the case of multidomain proteins, paramagnetic restraints can provide the correct mutual orientations and positions of domains in solution, as well as information on the conformational variability experienced by the macromolecule.
长程核磁共振约束，如抗磁剩余偶极耦合和顺磁数据，可用于确定大分子的三维结构。它们还可用于通过验证或“校正”晶体模型来监测并可能提高溶液中大分子结构的准确性。由于晶体结构受到晶体堆积力的影响，它们可能不是溶液中大分子结构的准确模型。然而，应通过同时使用晶体和溶液核磁共振数据对结构进行精修来检验实际差异的存在。为实现这一点，对CCP4中的REFMAC5程序进行了修改，以允许同时使用X射线晶体学和顺磁核磁共振数据及/或抗磁剩余偶极耦合。晶体结构与溶液核磁共振数据之间的不一致（如有），可能是由于从溶液态转变为固态时发生的结构重排，或者是由于溶液中相对于晶体存在更大程度的构象异质性。对于多结构域蛋白质，顺磁约束可提供溶液中各结构域的正确相互取向和位置，以及有关大分子所经历的构象变异性的信息。
