Massey D E, Smyth D G
J Biol Chem. 1975 Aug 25;250(16):6288-90.
The amino acid sequence of the proinsulin C-peptide isolated from guinea pig pancreas was determined and experimental data are presented. Digestion of the C-peptide with chymotrypsin provided two dodecapeptides, a tetrapeptide, and glutamine, which account for the intact chain. Reaction of the C-peptide with cyanogen bromide resulted in cleavage at the single methionine and provided two additional fragments. Digestion of the large peptides with papain provided a variety of small peptides and the complete sequence was assigned by identification of the fragments. Although guinea pig insulin differs markedly from mammalian insulins, guinea pig C-peptide has many features of primary structure in common with the C-peptides of other mammals. The conservation of specific residues in C-peptides indicates that these residues form essential elements in the three-dimensional structure of proinsulin.
测定了从豚鼠胰腺分离出的胰岛素原C肽的氨基酸序列，并给出了实验数据。用胰凝乳蛋白酶消化C肽得到两个十二肽、一个四肽和谷氨酰胺，它们构成了完整的链。C肽与溴化氰反应导致在单个甲硫氨酸处裂解，并产生另外两个片段。用木瓜蛋白酶消化大肽得到各种小肽，并通过片段鉴定确定了完整序列。尽管豚鼠胰岛素与哺乳动物胰岛素有显著差异，但豚鼠C肽在一级结构上与其他哺乳动物的C肽有许多共同特征。C肽中特定残基的保守性表明这些残基构成了胰岛素原三维结构中的基本元素。
