Wang Xi, Yu Binhan, Wang Tianzhi, Iwahara Junji
Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas 77555-1068, United States.
J Phys Chem Lett. 2025 Mar 6;16(9):2175-2180. doi: 10.1021/acs.jpclett.4c03666. Epub 2025 Feb 20.
Although nuclear magnetic resonance (NMR) spectroscopy is powerful for protein dynamics investigations, the anisotropy of internal motions has been difficult to analyze with NMR. In principle, NMR order parameters for multiple bond vectors fixed on the same plane can reveal the anisotropy of internal motions. We investigated the anisotropic dynamics of protein asparagine (Asn) and glutamine (Gln) side chain NH groups using H and N NMR relaxation rates. Hindered rotations about the C-N bond causing chemical exchange between the two hydrogens of Asn/Gln NH groups are far slower than H relaxation. Using the H and N relaxation data at two magnetic fields, we determined two order parameters and H quadrupolar coupling constants for each NH group of ubiquitin. Our data clearly illuminate the heterogeneous dynamic properties of the protein side chain NH groups with different degrees of the motional anisotropy, which depends strongly on the local environment.
尽管核磁共振（NMR）光谱在蛋白质动力学研究方面功能强大，但内部运动的各向异性一直难以用NMR进行分析。原则上，固定在同一平面上的多个键向量的NMR序参数可以揭示内部运动的各向异性。我们使用H和N NMR弛豫率研究了蛋白质天冬酰胺（Asn）和谷氨酰胺（Gln）侧链NH基团的各向异性动力学。围绕C-N键的受阻旋转导致Asn/Gln NH基团的两个氢之间发生化学交换，其速度远慢于H弛豫。利用两个磁场下的H和N弛豫数据，我们确定了泛素每个NH基团的两个序参数和H四极耦合常数。我们的数据清楚地阐明了具有不同程度运动各向异性的蛋白质侧链NH基团的异质动力学特性，这在很大程度上取决于局部环境。
