Miyata S, Akazawa T
Proc Natl Acad Sci U S A. 1982 Nov;79(21):6566-8. doi: 10.1073/pnas.79.21.6566.
During the biosynthesis of secretory proteins, an NH2-terminal peptide, referred to as a signal peptide, is cotranslationally cleaved off after the protein enters the cisternal space of the endoplasmic reticulum. It also has been reported that the core glycosylation reaction of some secretory and viral membrane glycoproteins occurs as a cotranslational event. However, despite a huge amount of work, no decisive answer has been given as to the temporal sequence of proteolytic cleavage of the signal peptide and glycosylation on the polysomes for any secretory or membrane glycoprotein. We show here that proteolytically processed and already glycosylated chains of rice seed alpha-amylase exist on the polysomes; furthermore, our results provide direct evidence that glycosylation is preceded by proteolytic processing during the biosynthesis of the alpha-amylase molecule.
在分泌蛋白的生物合成过程中，一个氨基末端肽，即信号肽，在蛋白质进入内质网的潴泡腔后共翻译时被切割掉。也有报道称，一些分泌性和病毒膜糖蛋白的核心糖基化反应是作为共翻译事件发生的。然而，尽管进行了大量研究工作，但对于任何分泌性或膜糖蛋白，信号肽的蛋白水解切割和多核糖体上糖基化的时间顺序仍未给出决定性答案。我们在此表明，水稻种子α-淀粉酶经蛋白水解加工且已糖基化的链存在于多核糖体上；此外，我们的结果提供了直接证据，即在α-淀粉酶分子的生物合成过程中，糖基化发生在蛋白水解加工之前。
