Determination of phi and chi(1) angles in proteins from C-13-C-13 three-bond J couplings measured by three-dimensional heteronuclear NMR. How planar is the peptide bond?
Determination of phi and chi(1) angles in proteins from C-13-C-13 three-bond J couplings measured by three-dimensional heteronuclear NMR. How planar is the peptide bond?
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DOI：
10.1021/ja970067v
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发表时间：
1997-07-09
影响因子：
15
通讯作者：
Bax, A
中科院分区：
文献类型：
--
作者：
Hu, JS;Bax, A
本文介绍了一种新的脉冲方案HN（CO）C，用于同时测量均匀富集C-13和N-15的蛋白质中的三键3 J（C 'C β）和3 J（C' C γ）偶合。实验证明，为人类泛素和脱辅基钙调蛋白，旋转相关时间分别为4和8纳秒。通过将泛素3 J（C ′ C β）值与其晶体结构的骨架φ角相关联，获得了Karplus关系，3 J（C ′ C β）= 1.59 cos（2）（φ-120度）-0.67 cos（φ-120度）+0.27 Hz。使用这些晶体结构phi角，实验3 J（C 'C β）值和从Karplus关系预测的值之间的均方根差（rmsd）为0.24 Hz。当使用从3 J（HNH alpha）、3 J（HNC beta）、3（JHC）、3（JH alpha C '）和3 J（C' C '）导出的phi角时，该rmsd减小到0.17 Hz。肽骨架phi角可以衍生自C 'i-1或H-i（N）与三个C-i（α）取代基C'（i）、C-i（β）、H-i（α）之间的J偶联。对于泛素中的45个残基，在所有六个偶联中都已经测量，从涉及H-1（N）的偶联的这些残基得到的phi角与从三个J偶联到C ′（i-1）得到的phi角在实验误差（rmsd = 7.7度）内一致。这证实，平均而言，C ′（i-1）-N-i-C-i（α）和H-i（N）-N-i-C-i（α）平面之间的角度显著小于7.7度，并且排除了α-螺旋中与肽键平面性大偏差的可能性。残基（3）J（C ′ C γ）内，脂肪族残基的偶联频率范围为0.7 Hz（对于一种交错构象）到约4 Hz（对于一种反式构象）。
A new pulse scheme, HN(CO)C, is described for simultaneous measurement of three-bond 3J(C'C beta) and 3J(C'C gamma) couplings in proteins uniformly enriched with C-13 and N-15. The experiment is demonstrated for human ubiquitin and apo-calmodulin, which have rotational correlation times of 4 and 8 ns, respectively. A Karplus relation, 3J(C'C beta) = 1.59 cos(2)(phi-120 degrees) - 0.67 cos(phi-120 degrees) + 0.27 Hz, is obtained by correlating the ubiquitin 3J(C'C beta) values with backbone phi angles from its crystal structure. Using these crystal structure phi angles, the root-mean-square difference (rmsd) between experimental 3J(C'C beta) values and those predicted from the Karplus relation is 0.24 Hz. When using phi angles derived from 3J(HNH alpha), 3J(HNC beta), 3(JHC), 3(JH alpha C'), and 3J(C'C'), this rmsd decreases to 0.17 Hz. Peptide backbone phi angles can be derived from J couplings between either C'i-1 or H-i(N) and the three C-i(alpha) substituents, C'(i), C-i(beta), H-i(alpha). For 45 residues in ubiquitin in all six couplings have been measured, the phi angles derived from these residues from couplings involving H-i(N) agree to within experimental error (rmsd = 7.7 degrees) with phi angles derived from the three J couplings to C'(i-1). This confirms that, on average, the angle between the C'(i-1)-N-i-C-i(alpha) and H-i(N)-N-i-C-i(alpha) planes is considerably less than 7.7 degrees and excludes the possibility of large deviations from peptide bond planarity in alpha-helices. Intraresidue (3)J(C'C gamma), couplings for aliphatic residues are found to range form 0.7 Hz for a gauche conformation to ca 4 Hz for a trans conformation.