Smith M E
Department of Neurology, VA Medical Center, Palo Alto, CA 94304.
Neurochem Res. 1994 Aug;19(8):1039-45. doi: 10.1007/BF00968714.
It has been known for some time that P0, the major intrinsic protein in PNS myelin, contains sulfate. The position of sulfate has been described for beef PNS myelin, but rat PNS myelin differs somewhat from that of the beef, therefore an investigation of the location of sulfate in rat P0 was undertaken. Weanling rat nerves were incubated with [3H] amino acid mixture and [35S]O4, and purified myelin was prepared, and the proteins separated on polyacrylamide gels. The bulk of the [35S]O4 was incorporated into P0, but smaller peaks of sulfate label were found in the higher molecular weight proteins. With tunicamycin in the incubation mixture, sulfate incorporation was inhibited. Incubation of the labeled myelin mixture with endo F or glycanase resulted in total loss of sulfate label on P0, therefore all of the [35S]O4 was incorporated into the oligosaccharide chain, with none on the polypeptide. Castanospermine and deoxymannojirimycin inhibited [35S]O4 incorporation into P0, but no inhibition was exerted by swainsonine. These results indicate that sulfate resides in the core of the oligosaccharide chain, with none in the terminal region. Such a structure would correlate with the lack of an HNK-1 epitope, absent in the rat, but found in P0 of many species.
一段时间以来，人们已经知道周围神经系统（PNS）髓鞘中的主要内在蛋白P0含有硫酸盐。牛肉PNS髓鞘中硫酸盐的位置已有描述，但大鼠PNS髓鞘与牛肉的有所不同，因此对大鼠P0中硫酸盐的位置进行了研究。将断奶大鼠的神经与[3H]氨基酸混合物和[35S]O4一起孵育，制备纯化的髓鞘，并在聚丙烯酰胺凝胶上分离蛋白质。大部分[35S]O4掺入到P0中，但在较高分子量的蛋白质中发现了较小的硫酸盐标记峰。在孵育混合物中加入衣霉素，硫酸盐掺入受到抑制。用内切糖苷酶F或聚糖酶孵育标记的髓鞘混合物会导致P0上的硫酸盐标记完全消失，因此所有[35S]O4都掺入到寡糖链中，多肽上没有。栗精胺和脱氧甘露基野尻霉素抑制[35S]O4掺入P0，但苦马豆素没有抑制作用。这些结果表明硫酸盐存在于寡糖链的核心，末端区域没有。这样的结构与大鼠缺乏HNK-1表位相关，HNK-1表位在许多物种的P0中存在，但在大鼠中不存在。
