Faissner A, Teplow D B, Kübler D, Keilhauer G, Kinzel V, Schachner M
EMBO J. 1985 Dec 1;4(12):3105-13. doi: 10.1002/j.1460-2075.1985.tb04052.x.
The biosynthesis and membrane topography of the neural cell adhesion molecule L1 have been studied in cerebellar cell cultures by metabolic labeling and immunoprecipitation. Pulse and pulse-chase experiments with [35S]methionine show that L1 is synthesized in its high mol. wt. form, the 200 kd component. The lower mol. wt. components with 40, 80 and 140 K apparent mol. wts. can be generated by proteolysis in intact cellular membranes. Peptide maps generated by protease treatment of L1 isolated from adult mouse brain show that the 80 and 140 kd components are related to the 200 kd component, but not to each other. The 200, 80 and 40 kd components can be biosynthetically phosphorylated. The 140 kd component is not phosphorylated and not released from the surface membrane during tryspinization. The phosphorylated amino acid is serine. In the presence of tunicamycin the 200 kd component is synthesized as a 150 kd protein. Pulse-chase experiments in the presence of tunicamycin indicate that the carbohydrate moieties are predominantly N-glycosidically linked and that the contribution of O-glycosylation is minimal. The carbohydrate moieties are of the complex type as shown by treatment with endoglycosidase H. Since monensin inhibits processing of the carbohydrate moieties, the 200 kd component appears to be transported to the surface membrane via the Golgi apparatus.
通过代谢标记和免疫沉淀技术，在小脑细胞培养物中研究了神经细胞粘附分子L1的生物合成和膜拓扑结构。用[35S]甲硫氨酸进行脉冲和脉冲追踪实验表明，L1以其高分子量形式即200kd组分合成。具有40、80和140K表观分子量的较低分子量组分可通过完整细胞膜中的蛋白水解产生。用蛋白酶处理从成年小鼠脑分离的L1所产生的肽图表明，80kd和140kd组分与200kd组分相关，但彼此不相关。200kd、80kd和40kd组分可进行生物合成磷酸化。140kd组分不被磷酸化，在胰蛋白酶处理期间不从表面膜释放。磷酸化氨基酸是丝氨酸。在衣霉素存在下，200kd组分作为150kd蛋白质合成。在衣霉素存在下的脉冲追踪实验表明，碳水化合物部分主要是N-糖苷键连接的，O-糖基化的贡献最小。如用内切糖苷酶H处理所示，碳水化合物部分是复合型的。由于莫能菌素抑制碳水化合物部分的加工，200kd组分似乎通过高尔基体转运到表面膜。
