Cowan E P, Cummings R D, Schwartz B D, Cullen S E
J Biol Chem. 1982 Oct 10;257(19):11241-8.
Murine Ia antigens consist of two glycosylated polypeptide chains, the alpha chain and the beta chain. We have used lectin affinity chromatography to confirm previous work in our laboratory that three distinct, differentially glycosylated I-Ak alpha chains (alpha 1, alpha 2, and alpha 3) exist and to compare the carbohydrate of the alpha chain with that of the beta chain. Glycopeptides derived from pronase digestion of [3H]mannose-labeled I-Ak alpha 1, alpha 2, alpha 3, and beta chains were sequentially passed over columns of immobilized concanavalin A, Lens culinaris lectin, phytohemagglutinin-E, and phytohemagglutinin-L in a prescribed manner to generate a lectin affinity profile, which, in turn, allowed assignment of a minimal oligosaccharide structure for each glycopeptide studied. The lectin affinity profile for each chain was unique. The alpha 1, alpha 2, and beta chains each possess complex-type N-linked oligosaccharides, although the branching pattern and specific sugar residues found on each differ. The alpha 3 chain, on the other hand, possesses predominantly high mannose or hybrid-type N-linked oligosaccharides. Lectin affinity analysis of glycopeptides derived from pronase digestion of high pressure liquid chromatography-isolated tryptic-chymotryptic fragments from alpha 2 and alpha 3 and tryptic fragments from beta revealed that specific minimal oligosaccharide structures were associated with particular fragments. In addition, although tryptic-chymotryptic peptide maps of alpha 2 and alpha 3 were similar, alpha 2 fragments bear predominantly complex-type N-linked oligosaccharides, whereas homologous alpha 3 fragments bear high mannose or hybrid-type N-linked oligosaccharides. Possible explanations of the oligosaccharide heterogeneity are discussed.
小鼠Ia抗原由两条糖基化多肽链组成，即α链和β链。我们利用凝集素亲和层析法证实了我们实验室之前的研究成果，即存在三种不同的、糖基化程度不同的I-Akα链（α1、α2和α3），并比较了α链和β链的碳水化合物。将源自[3H]甘露糖标记的I-Akα1、α2、α3和β链经链霉蛋白酶消化得到的糖肽，按照规定的方式依次通过固定化伴刀豆球蛋白A、扁豆凝集素、植物血凝素-E和植物血凝素-L柱，以生成凝集素亲和图谱，进而为每个研究的糖肽确定最小寡糖结构。每条链的凝集素亲和图谱都是独特的。α1、α2和β链均具有复合型N-连接寡糖，尽管每条链上的分支模式和特定糖残基有所不同。另一方面，α3链主要具有高甘露糖型或杂合型N-连接寡糖。对源自高压液相色谱分离的α2和α3的胰蛋白酶-糜蛋白酶片段以及β链的胰蛋白酶片段经链霉蛋白酶消化得到的糖肽进行凝集素亲和分析，结果表明特定的最小寡糖结构与特定片段相关。此外，尽管α2和α3的胰蛋白酶-糜蛋白酶肽图相似，但α2片段主要带有复合型N-连接寡糖，而同源的α3片段则带有高甘露糖型或杂合型N-连接寡糖。文中讨论了寡糖异质性的可能解释。
