Szyperski T, Luginbühl P, Otting G, Güntert P, Wüthrich K
Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule-Hönggerberg, Zürich, Switzerland.
J Biomol NMR. 1993 Mar;3(2):151-64. doi: 10.1007/BF00178259.
Conformational rate processes in aqueous solutions of uniformly 15N-labeled pancreatic trypsin inhibitor (BPTI) at 36 degrees C were investigated by measuring the rotating frame relaxation times of the backbone 15N spins as a function of the spin-lock power. Two different intramolecular exchange processes were identified. A first local rate process involved the residues Cys38 and Arg39, had a correlation time of about 1.3 ms, and was related to isomerization of the chirality of the disulfide bond Cys14-Cys38. A second, faster motional mode was superimposed on the disulfide bond isomerization and was tentatively attributed to local segmental motions in the polypeptide sequence -Cys14-Ala15-Lys16-. The correlation time for the overall rotational tumbling of the protein was found to be 2 ns, using the assumption that relaxation is dominated by dipolar coupling and chemical shift anisotropy modulated by isotropic molecular reorientation.
通过测量主链15N自旋的旋转框架弛豫时间作为自旋锁定功率的函数，研究了在36摄氏度下均匀15N标记的胰腺胰蛋白酶抑制剂（BPTI）水溶液中的构象速率过程。确定了两种不同的分子内交换过程。第一个局部速率过程涉及Cys38和Arg39残基，相关时间约为1.3毫秒，并且与二硫键Cys14-Cys38的手性异构化有关。第二个更快的运动模式叠加在二硫键异构化上，并初步归因于多肽序列-Cys14-Ala15-Lys16-中的局部片段运动。假设弛豫由偶极耦合和由各向同性分子重取向调制的化学位移各向异性主导，发现蛋白质整体旋转翻滚的相关时间为2纳秒。
