Nicot C, Vacher M, Denoroy L, Kahn P C, Waks M
Biomédicale des Saints-Pères, Laboratoire des Systèmes Moléculaires Organisés, Paris, France.
J Neurochem. 1993 Apr;60(4):1283-91. doi: 10.1111/j.1471-4159.1993.tb03288.x.
We have investigated the early steps of myelin basic protein (MBP) degradation in a membrane mimetic system (reverse micelles), resembling the interlamellar aqueous spaces where the protein is located in the myelin sheath. MBP, unfolded in buffer, refolds on incorporation into the micelles, resulting in reduced accessibility to three proteolytic enzymes, trypsin, cathepsin D, and Staphylococcus aureus V8 protease, in comparison with aqueous solution. Eleven cleavage sites seen in buffer are removed from proteolytic attack in micellar solution. These sites delineate a protected protein domain displaying a potential beta-sheet structure capable of interacting with the myelin membrane. An additional site not seen in buffer is attacked in the micelles. Experiments with a structure inducer, 15% 1-propanol in buffer, reveal that the refolding pattern of MBP in reverse micelles is specific to the membrane biomimetic system and is not produced by organic solvent per se. Micellar digestions of MBP generate long peptides, two of which, isolated after tryptic digestion, have been found to be immunodominant in multiple sclerosis patients. The findings suggest the structure induced in MBP by the micelles resembles that leading to production of the self-peptides recognized by T cells during proteolytic breakdown of MBP in autoimmune demyelinating diseases.
我们在一个模拟膜系统（反胶束）中研究了髓鞘碱性蛋白（MBP）降解的早期步骤，该系统类似于髓鞘中蛋白质所在的片层间水相空间。在缓冲液中展开的MBP在掺入胶束时会重新折叠，与水溶液相比，这导致其对三种蛋白水解酶（胰蛋白酶、组织蛋白酶D和金黄色葡萄球菌V8蛋白酶）的可及性降低。在缓冲液中可见的11个切割位点在胶束溶液中免受蛋白水解攻击。这些位点划定了一个受保护的蛋白质结构域，该结构域显示出能够与髓鞘膜相互作用的潜在β-折叠结构。在缓冲液中未见的另一个位点在胶束中受到攻击。用结构诱导剂（缓冲液中15%的1-丙醇）进行的实验表明，MBP在反胶束中的重新折叠模式是膜仿生系统特有的，并非由有机溶剂本身产生。MBP的胶束消化产生长肽，其中两个在胰蛋白酶消化后分离出来，已被发现在多发性硬化症患者中具有免疫优势。这些发现表明，胶束在MBP中诱导的结构类似于自身免疫性脱髓鞘疾病中MBP蛋白水解分解过程中导致T细胞识别的自身肽产生的结构。
