Nehrke K, Tabak L A
Department of Dental Research, School of Medicine and Dentistry, University of Rochester, 601 Elmwood Avenue, Box 611, Rochester, NY 14642, USA.
Biochem J. 1997 Apr 15;323 ( Pt 2)(Pt 2):497-502. doi: 10.1042/bj3230497.
We have examined the biosynthesis of a low-molecular-mass mucin from rat submandibular gland (RSMG) expressed recombinantly in COS7 tissue culture cells, focusing primarily on the addition of carbohydrate to the protein core of the mucin. We find evidence for N-linked glycosylation, but this modification is not required for secretion of the mucin. Similarly, although the recombinant RSMG mucin, like its native counterpart, contains large amounts of O-linked carbohydrate, chain extension beyond the initial O-linked GalNAc moiety is not required for secretion. We have identified partially glycosylated mucin by a combination of metabolic pulse-chase and lectin precipitations of the biosynthetic intermediates. Our results suggest that the addition of GalNAc to threonine and serine in the RSMG mucin does not occur simultaneously, as has been described for other O-glycosylated proteins.
我们研究了在COS7组织培养细胞中重组表达的大鼠下颌下腺低分子量粘蛋白（RSMG）的生物合成，主要关注粘蛋白蛋白核心上碳水化合物的添加。我们发现了N-连接糖基化的证据，但这种修饰对于粘蛋白的分泌并非必需。同样，尽管重组RSMG粘蛋白与其天然对应物一样含有大量的O-连接碳水化合物，但分泌并不需要在初始O-连接的GalNAc部分之外进行链延伸。我们通过代谢脉冲追踪和生物合成中间体的凝集素沉淀相结合的方法鉴定了部分糖基化的粘蛋白。我们的结果表明，RSMG粘蛋白中苏氨酸和丝氨酸上GalNAc的添加并非如其他O-糖基化蛋白那样同时发生。
