Agrawal H C, Noronha A B, Agrawal D, Quarles R H
Department of Pediatrics, Washington University School of Medicine, St. Louis, MO.
Biochem Biophys Res Commun. 1990 Jun 29;169(3):953-8. doi: 10.1016/0006-291x(90)91986-3.
Phosphorylation of the myelin-associated glycoprotein (MAG) in the peripheral nervous system is demonstrated by immunoprecipitation from myelin proteins radiolabeled in vivo, in nerve slices and in a cell-free system. Phosphoamino acid analysis of immunoprecipitated MAG revealed the presence of radioactivity in phosphoserine, but not in phosphothreonine or phosphotyrosine. Only the shorter isoform of MAG (S-MAG) was detected by immunostaining of nitrocellulose sheets with anti-MAG anti-serum after enzymatic deglycosylation of immunoprecipitated MAG labeled in nerve slices. Autoradiography of the same Western blots revealed that most of the radioactive phosphate was in S-MAG, demonstrating that the polypeptide backbone of S-MAG is phosphorylated in the PNS.
通过对体内放射性标记的髓磷脂蛋白、神经切片和无细胞系统中进行免疫沉淀，证实了外周神经系统中髓磷脂相关糖蛋白（MAG）的磷酸化。对免疫沉淀的MAG进行磷酸氨基酸分析显示，磷酸丝氨酸中存在放射性，但磷酸苏氨酸或磷酸酪氨酸中不存在。在用抗MAG抗血清对经酶解去糖基化的神经切片中标记的免疫沉淀MAG进行硝酸纤维素膜免疫染色后，仅检测到较短的MAG同工型（S-MAG）。相同蛋白质印迹的放射自显影显示，大部分放射性磷酸盐存在于S-MAG中，表明S-MAG的多肽主链在外周神经系统中被磷酸化。
