Smith G M, Pettigrew G W
Eur J Biochem. 1980 Sep;110(1):123-30. doi: 10.1111/j.1432-1033.1980.tb04847.x.
The N-terminal tryptic peptide of Crithidia oncopelti cytochrome c557 X-Pro-Me3Lys-Ala-Arg in which X represents an unknown N-terminal blocking group was characterized by electrophoresis at pH 2 and by 1H and 13C nuclear magnetic resonance. 1H-NMR spectra of the tryptic peptide suggested that the blocking group X was N,N-dimethylproline although the electrophoretic mobility of the peptide suggested a larger molecular weight. The peptides X-Pro-Me3Lys and X-Pro were generated by treatment of the tryptic peptide with thermolysin and carboxypeptidase and the free blocking group X was prepared by acid hydrolysis. Comparison of the 1H-NMR spectra of these peptides with spectra of synthetic N,N-dimethylproline and N,N-dimethylprolylproline demonstrated that the blocking group was indeed N,N-dimethylproline. The 13C-NMR spectrum of the tryptic peptide was consistent with this conclusion although unambiguous assignments to all resonances could not be obtained because of the small amount of material available. The origin of the dimethylproline blocking group is discussed.
克氏锥虫细胞色素c557的N端胰蛋白酶肽X-Pro-Me3Lys-Ala-Arg（其中X代表未知的N端封闭基团）通过在pH 2下的电泳以及1H和13C核磁共振进行了表征。胰蛋白酶肽的1H-NMR光谱表明封闭基团X是N，N-二甲基脯氨酸，尽管该肽的电泳迁移率表明分子量更大。通过用嗜热菌蛋白酶和羧肽酶处理胰蛋白酶肽生成了肽X-Pro-Me3Lys和X-Pro，并且通过酸水解制备了游离的封闭基团X。将这些肽的1H-NMR光谱与合成的N，N-二甲基脯氨酸和N，N-二甲基脯氨酰脯氨酸的光谱进行比较，证明封闭基团确实是N，N-二甲基脯氨酸。胰蛋白酶肽的13C-NMR光谱与该结论一致，尽管由于可用材料量少，无法对所有共振进行明确归属。讨论了二甲基脯氨酸封闭基团的来源。
