Wishart D S, Sykes B D, Richards F M
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.
J Mol Biol. 1991 Nov 20;222(2):311-33. doi: 10.1016/0022-2836(91)90214-q.
An analysis of the 1H nuclear magnetic resonance chemical shift assignments and secondary structure designations for over 70 proteins has revealed some very strong and unexpected relationships. Similar studies, performed on smaller databases, for 13C and 15N chemical shifts reveal equally strong correlations to protein secondary structure. Among the more interesting results to emerge from this work is the finding that all 20 naturally occurring amino acids experience a mean alpha-1H upfield shift of 0.39 parts per million (from the random coil value) when placed in a helical configuration. In a like manner, the alpha-1H chemical shift is found to move downfield by an average of 0.37 parts per million when the residue is placed in a beta-strand or extended configuration. Similar changes are also found for amide 1H, carbonyl 13C, alpha-13C and amide 15N chemical shifts. Other relationships between chemical shift and protein conformation are also uncovered; in particular, a correlation between helix dipole effects and amide proton chemical shifts as well as a relationship between alpha-proton chemical shifts and main-chain flexibility. Additionally, useful relationships between alpha-proton chemical shifts and backbone dihedral angles as well as correlations between amide proton chemical shifts and hydrogen bond effects are demonstrated.
对70多种蛋白质的1H核磁共振化学位移归属和二级结构指定进行分析后，发现了一些非常强烈且出乎意料的关系。对较小数据库中13C和15N化学位移进行的类似研究表明，它们与蛋白质二级结构也存在同样强烈的相关性。这项工作得出的更有趣的结果之一是，发现所有20种天然存在的氨基酸在形成螺旋构象时，其平均α-1H向高场位移0.39 ppm（相对于无规卷曲值）。同样地，当残基处于β-链或伸展构象时，α-1H化学位移平均向低场移动0.37 ppm。酰胺1H、羰基13C、α-13C和酰胺15N化学位移也有类似变化。还发现了化学位移与蛋白质构象之间的其他关系；特别是，螺旋偶极效应与酰胺质子化学位移之间的相关性，以及α-质子化学位移与主链柔韧性之间的关系。此外，还证明了α-质子化学位移与主链二面角之间的有用关系，以及酰胺质子化学位移与氢键效应之间的相关性。
