Chan S J, Keim P, Steiner D F
Proc Natl Acad Sci U S A. 1976 Jun;73(6):1964-8. doi: 10.1073/pnas.73.6.1964.
Whole nucleic acid fractions of isolated rat islets of Langerhans greatly stimulate incorporation of radioactive amino acids into protein in a wheat germ ribosomal system. Approximately 30% of the synthetic product is precipitated with antisera to insulin or proinsulin. Characterization of this material by gel chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicates a molecular mass of 11,500 daltons. Trypsin digestion releases intact A chain as well as tryptic fragments of the C-peptides and B chains of the two rat proinsulins. Automated sequence determination of labeled cell-free product purified by immunoprecipitation discloses the presence of 23 additional amino acids NH2-terminal to the B chain sequence of proinsulin. The partial amino acid sequence of this extension is as follows: NH2-X-Leu (Lys) Met-x-Phe-Leu-Phe-Leu-Leu (Lys) Leu-Leu-x-leu-X-X-X-X-X-X-X-X-proinsulin. On the basis of the above evidence we have designated this peptide preproinsulin.
分离出的大鼠胰岛的全核酸组分能极大地刺激放射性氨基酸在麦胚核糖体系统中掺入蛋白质。约30%的合成产物能用抗胰岛素或胰岛素原的抗血清沉淀。通过凝胶色谱法和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳对该物质进行表征，结果表明其分子量为11,500道尔顿。胰蛋白酶消化可释放出完整的A链以及两种大鼠胰岛素原C肽和B链的胰蛋白酶片段。对通过免疫沉淀纯化的标记无细胞产物进行自动序列测定，结果显示在胰岛素原B链序列的氨基末端还存在另外23个氨基酸。该延伸序列的部分氨基酸序列如下：NH2-X-亮氨酸（赖氨酸）-甲硫氨酸-x-苯丙氨酸-亮氨酸-苯丙氨酸-亮氨酸-亮氨酸（赖氨酸）-亮氨酸-亮氨酸-x-亮氨酸-X-X-X-X-X-X-X-X-胰岛素原。基于上述证据，我们将此肽命名为前胰岛素原。
