Sun W Y, Xiong J, Shulman M J
Department of Immunology, University of Toronto, Canada.
Biochem Biophys Res Commun. 1991 Sep 30;179(3):1627-34. doi: 10.1016/0006-291x(91)91761-z.
Previous work suggested that the substitution of Asn for Ser at position 406 of the mu heavy chain of mouse IgM results in aberrant glycosylation at Asn402. In order to characterise the apparently abnormal glycosylation process more precisely, the mutant and wildtype mu chains were fragmented by cleavage with cyanogen bromide, and the resulting glycopeptides were analysed further. Measurements of lectin binding specificity as well as glycosidase sensitivity suggest that the oligosaccharide at Asn402 of wildtype mu is a hybrid type which does not contain terminal alpha(2-6) or alpha(2-3) linked sialic acid. By contrast, the corresponding oligosaccharide on Asn402 of mutant mu is complex and contains terminal sialic acid linked alpha(2-6) to galactose. The structural features for specifying the abnormal glycosylation are present in monomeric mutant IgM.
先前的研究表明，小鼠IgM μ重链第406位的丝氨酸被天冬酰胺取代会导致Asn402处糖基化异常。为了更精确地表征这种明显异常的糖基化过程，用溴化氰裂解突变型和野生型μ链，对产生的糖肽进行进一步分析。凝集素结合特异性和糖苷酶敏感性的测量结果表明，野生型μ链Asn402处的寡糖是杂合型，不含有末端α(2-6)或α(2-3)连接的唾液酸。相比之下，突变型μ链Asn402处的相应寡糖是复合型，含有末端唾液酸通过α(2-6)连接到半乳糖。决定异常糖基化的结构特征存在于单体突变型IgM中。
