Wüthrich K, Wagner G, Richarz R, Perkins S J
Biochemistry. 1978 Jun 13;17(12):2253-63. doi: 10.1021/bi00605a001.
In earlier work the resonances of the 20 methyl groups in the basic pancreatic trypsin inhibitor (BPTI) had been identified in the 360-MHz 1H nuclear magnetic resonance (NMR) spectra and most of the methyl lines had from spin-decoupling experiments been assigned to the different types of amino acid residues. The assignments to the different amino acid types were now completed by studies of the saturation transfer between the denatured and the globular forms of the inhibitor and by spin-decoupling experiments in nuclear Overhauser enhancement (NOE) difference spectra. These distinguished between the methyl resonances of Ala and Thr. Furthermore, for most of the methyl resonances, individual assignments to specific residues in the amino acid sequence were obtained from measurements of intramolecular proton-proton NOE's, use of lanthanide NMR shift and relaxation probes, and comparative studies of various chemically modified forms of BPTI. These data provide the basis for individual assignments of the methyl 13C NMR lines in BPTI and for detailed investigations of the relations between the spatial structure of the protein and the chemical shifts of the methyl groups. The methyl groups in BPTI are of particular interest since they are located almost exclusively on the surface of the protein and thus represent potential natural NMR probes for studies of the protein-protein interactions in the complexes formed between BPTI and a variety of proteases.
在早期的工作中，已在360兆赫的1H核磁共振（NMR）谱中鉴定出碱性胰蛋白酶抑制剂（BPTI）中20个甲基的共振信号，并且通过自旋去耦实验已将大多数甲基谱线归属于不同类型的氨基酸残基。现在，通过研究抑制剂变性形式与球状形式之间的饱和转移以及核Overhauser增强（NOE）差谱中的自旋去耦实验，完成了对不同氨基酸类型的归属。这些实验区分了丙氨酸和苏氨酸的甲基共振信号。此外，对于大多数甲基共振信号，通过测量分子内质子-质子NOE、使用镧系元素NMR位移和弛豫探针以及对BPTI各种化学修饰形式的比较研究，获得了氨基酸序列中特定残基的个别归属。这些数据为BPTI中甲基13C NMR谱线的个别归属以及详细研究蛋白质的空间结构与甲基化学位移之间的关系提供了基础。BPTI中的甲基特别受关注，因为它们几乎全部位于蛋白质表面，因此代表了潜在的天然NMR探针，可用于研究BPTI与多种蛋白酶形成的复合物中的蛋白质-蛋白质相互作用。
