Nilges M, Clore G M, Gronenborn A M
Laboratory of Chemical Physics, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institute of Health, Bethesda, Maryland 20892.
Biopolymers. 1990 Mar-Apr;29(4-5):813-22. doi: 10.1002/bip.360290415.
A search procedure is described for making stereospecific assignments at prochiral centers in proteins on the basis of nuclear Overhauser enhancement and coupling constant data derived from nmr experiments. A data base comprising torsion angles, associated 1H-1H coupling constants and interproton distances is searched by a computer algorithm for sets of values that match the experimental data within specified error limits. Two different data bases are used. The first is a crystallographic data base derived from 34 well-refined crystal structures; the second is a systematic data base derived from conformations of a short peptide fragment with idealized geometry by systematically varying the phi, psi, and chi 1 torsion angles. Both approaches are tested for beta-methylene groups with model data obtained from 20 crystal structures. The results for the two methods are similar though not identical, so that a combination of the two methods appears to be useful. With an appropriate choice of error estimates, around 80% of the beta-methylene groups could be assigned in the test calculations. In addition, results with experimental nmr data indicate that a similar percentage of stereospecific assignments can be made in practical situations.
本文描述了一种搜索程序，该程序基于核磁共振实验得出的核Overhauser效应增强和耦合常数数据，对手性前体中心在蛋白质中的立体专一性归属进行确定。通过计算机算法在包含扭转角、相关的1H-1H耦合常数和质子间距离的数据库中搜索，以找出在指定误差范围内与实验数据匹配的数值集。使用了两个不同的数据库。第一个是源自34个精修晶体结构的晶体学数据库；第二个是通过系统改变phi、psi和chi 1扭转角，从具有理想化几何结构的短肽片段构象中得出的系统数据库。两种方法都用从20个晶体结构获得的模型数据对β-亚甲基基团进行了测试。两种方法的结果相似但不完全相同，因此两种方法的结合似乎很有用。通过适当选择误差估计，在测试计算中约80%的β-亚甲基基团可以被归属。此外，实验核磁共振数据的结果表明，在实际情况下可以进行类似比例的立体专一性归属。
