MacDonald R J, Przybyla A E, Rutter W J
J Biol Chem. 1977 Aug 10;252(15):5522-8.
RNA prepared from dog pancreas polysomes or microsomes directs the synthesis of pancreas-specific proteins in heterologous cell-free translation systems. A translation product, approximately 1500 daltons larger than authentic amylase, corresponding to pancreatic amylase was identified by immunoprecipitation with anti-amylase gamma-globulin and tryptic peptide analysis. We suggest that this larger form of amylase is an amylase precursor. Using amylase immunoprecipitation of reticulocyte translation reactions as an assay, we have shown that greater than 99% of the mRNA for amylase is associated with polysomes bound to the endoplasmic reticulum. Electrophoresis of pancreatic mRNA preparations in formamide-containing polyacrylamide gels and subsequent translation of the fractions have shown that amylase mRNA is of a discrete size with a mobility equivalent to that of 18 S ribosomal RNA, and therefore significantly larger than required to code solely for the amino acid sequence of the amylase precursor.
从狗胰腺多核糖体或微粒体中制备的RNA，在异源无细胞翻译系统中指导胰腺特异性蛋白质的合成。通过用抗淀粉酶γ-球蛋白进行免疫沉淀和胰蛋白酶肽分析，鉴定出一种翻译产物，其比真实淀粉酶大约大1500道尔顿，对应于胰腺淀粉酶。我们认为这种更大形式的淀粉酶是淀粉酶前体。使用淀粉酶免疫沉淀网织红细胞翻译反应作为一种检测方法，我们已经表明，超过99%的淀粉酶mRNA与内质网结合的多核糖体相关。在含甲酰胺的聚丙烯酰胺凝胶中对胰腺mRNA制剂进行电泳，随后对各组分进行翻译，结果表明淀粉酶mRNA具有离散的大小，其迁移率与18S核糖体RNA相当，因此明显大于仅编码淀粉酶前体氨基酸序列所需的大小。
