Weimbs T, Stoffel W
Institute of Biochemistry, Medical Faculty, University of Cologne, Germany.
Biochemistry. 1994 Aug 30;33(34):10408-15. doi: 10.1021/bi00200a023.
Myelin proteolipid protein (PLP), the main integral membrane protein in the central nervous system myelin, was labeled at the extracytoplasmic domains with the membrane impermeant reagents pyridoxal 5'-phosphate and tritiated borohydride. Lysine-217, located in the fourth hydrophilic domain of PLP, was found to be the major labeled residue, which defined this domain to be extracytoplasmic in agreement with our previously proposed topological model. The remarkably high reactivity in vitro of this residue as compared to all other lysines in PLP led us to investigate the possible modification of PLP in vivo by other carbonyl compounds. We demonstrate that PLP is the most highly nonenzymatically glycosylated membrane protein in murine and bovine brain. The degree of modification increases significantly under hyperglycemic conditions, as studied in diabetic mice. The majority of the glycosylation sites are also located at extracytoplasmic domains. The degree of nonenzymatic glycosylation of PLP may be related to late diabetic complications affecting the central nervous system.
髓磷脂蛋白脂蛋白（PLP）是中枢神经系统髓磷脂中的主要整合膜蛋白，其胞外结构域用膜不透性试剂5'-磷酸吡哆醛和氚化硼氢化钠进行标记。位于PLP第四亲水结构域的赖氨酸-217被发现是主要的标记残基，这表明该结构域位于胞外，与我们之前提出的拓扑模型一致。与PLP中所有其他赖氨酸相比，该残基在体外具有极高的反应活性，这促使我们研究PLP在体内是否可能被其他羰基化合物修饰。我们证明，PLP是小鼠和牛脑中非酶糖基化程度最高的膜蛋白。在糖尿病小鼠中进行的研究表明，在高血糖条件下，修饰程度显著增加。大多数糖基化位点也位于胞外结构域。PLP的非酶糖基化程度可能与影响中枢神经系统的晚期糖尿病并发症有关。
