Whitehead J S, Remer L, Kim Y S
Biochim Biophys Acta. 1976 Jul 21;437(2):384-93. doi: 10.1016/0304-4165(76)90008-8.
Three glycopeptides have been isolated from the mucosal homogenates of the rat small intestine without using proteolysis. These glycopeptides appear to be localized exclusively in the membranes of the endoplasmic reticula. Although they have similar molecular weights of about 2550 and have similar amino acid compositions, they differ in the carbohydrate constituents. The major glycopeptide has 2 mol glucose per polypeptide chain while the two other glycopeptides contain 1 mol fucose, mannose and galactose with either 1 or 2 mol glucose. No hexosamine or sialic acid was detected in any of the glycopeptides. An unusual physical property was found associated with these glycopeptides. Below pH 6.5 they formed a precipitate which prevented them from diffusing through a dialysis membrane and allowed them to be rapidly purified following solubilization from the membrane. These glycopeptides appear to represent a new group of heretofore uncharacterized membrane constitutents which may play a role in some function specific for the endoplasmic reticula.
在未进行蛋白水解的情况下，已从大鼠小肠黏膜匀浆中分离出三种糖肽。这些糖肽似乎仅定位于内质网的膜中。尽管它们具有约2550的相似分子量且氨基酸组成相似，但碳水化合物成分有所不同。主要的糖肽每条多肽链含有2摩尔葡萄糖，而另外两种糖肽含有1摩尔岩藻糖、甘露糖和半乳糖，以及1或2摩尔葡萄糖。在任何一种糖肽中均未检测到己糖胺或唾液酸。发现这些糖肽具有一种不寻常的物理性质。在pH 6.5以下，它们会形成沉淀，这阻止了它们通过透析膜扩散，并使其在从膜中溶解后能够迅速纯化。这些糖肽似乎代表了一类迄今为止未被表征的新的膜成分，它们可能在内质网特有的某些功能中发挥作用。
