Shields D, Warren T G, Roth S E, Brenner M J
Nature. 1981 Feb 5;289(5797):511-4. doi: 10.1038/289511a0.
Glucagon, a polypeptide hormone of 29 amino acids, is synthesized in the islets of Langerhans and immunoreactive forms of the molecule have been found in several tissues. Like many other polypeptide hormones, glucagon is synthesized via a larger precursor molecular, proglucagon; however, estimates of its size vary considerably and the biosynthetic relationship between some of the putative precursors and authentic secreted glucagon is unclear. Consequently it was of interest to investigate the primary translation product of glucagon mRNA to relate its size to that of previously described glucagon precursors. Here we provide evidence for three distinct immunoreactive preproglucagon molecules, two of which have an apparent molecular weight (MW) of approximately 16,000 (16K). Furthermore, when microsomal membranes were present during translation, the nascent 14K preproglucagon polypeptides were processed to proglucagon with a higher apparent MW of 15,000. In contrast, the nascent 16K preproglucagon was co-translationally processed to a slightly smaller polypeptide. The data indicate that the 14K and 16K preproglucagons undergo different types of post-translational modification.
胰高血糖素是一种由29个氨基酸组成的多肽激素，在胰岛中合成，并且在多种组织中都发现了该分子的免疫反应形式。与许多其他多肽激素一样，胰高血糖素是通过一种更大的前体分子——前胰高血糖素原合成的；然而，其大小的估计差异很大，一些假定的前体与真正分泌的胰高血糖素之间的生物合成关系尚不清楚。因此，研究胰高血糖素mRNA的初级翻译产物，以将其大小与先前描述的胰高血糖素前体的大小相关联，是很有意义的。在这里，我们提供了三种不同的免疫反应性前胰高血糖素原分子的证据，其中两种的表观分子量（MW）约为16,000（16K）。此外，当翻译过程中存在微粒体膜时，新生的14K前胰高血糖素多肽会被加工成表观分子量更高的15,000的胰高血糖素原。相比之下，新生的16K前胰高血糖素会在共翻译过程中被加工成一个稍小的多肽。数据表明，14K和16K前胰高血糖素原经历了不同类型的翻译后修饰。
