MYELIN PO GLYCOPROTEIN: STRUCTURE & ADHESIVE MECHANISMS

描述（申请人摘要）：总体目标 本申请旨在定义髓磷脂的分子组织， 稳定其多层鞘的粘合机制，以及什么缺陷 在其组织和分子成分中可能导致髓鞘形成障碍， 脱髓鞘，例如发生在某些周围神经病和多种 硬化症该方法是基于X射线结果的相关性 晶体学和溶液散射、膜衍射和电子 显微镜具体目标，重点是结构和作用， 周围神经髓鞘的主要跨膜蛋白（P0-糖蛋白） （1）确定P0-糖蛋白的三维结构， 人类和非洲爪蟾分析的蛋白质将包括重组分子 具有天然氨基酸序列的那些，以及具有特异性氨基酸序列的那些， 已知在人类周围神经病变中发生的序列改变。这些 研究将告知P0的原子结构和晶体 接触或粘附界面，可能是负责这一作用， 蛋白质在髓鞘形成和稳定中的作用。(2)表征 蛋白质-蛋白质相互作用的最近邻P0分子在一个 膜模拟环境使用小角度X射线散射。膜 蛋白质将在非常低的温度下溶解在洗涤剂的水溶液中， 浓度和溶液散射将采用同步加速器 X射线源这些研究将提供有关蛋白质间的信息 P0分子在更紧密的环境中形成的分子接触 类似于其天然环境（髓鞘膜的脂质双层） 比水晶更有用(3)为了评价膜-膜相互作用， 爪蟾周围神经的髓鞘。确定pH值和离子 剥离外周血管中膜结构和填充的强度依赖性 在不同温度下培养的神经将提供强大的约束 为了测试关于P0在两个方向上的粘附机制的假设， 细胞质和细胞外膜并置。这种等级制度 实验目标将使研究者能够唯一地将 从原子到分子，再到膜水平的结构数据， 从而有助于理解膜的结构生物学 在健康和疾病中起重要作用的蛋白质。

DESCRIPTION (Applicant's abstract): The overall objective of this application is to define the molecular organization of myelin, the diverse adhesive mechanisms that stabilize its multilamellar sheath, and what defects in its organization and molecular constituents may lead to dysmyelination or demyelination such as occur in certain peripheral neuropathies and in multiple sclerosis. The approach is based on a correlation of results from X-ray crystallography and solution scattering, membrane diffraction, and electron microscopy. The specific aims, which are focused on the structure and role of the major transmembrane protein of peripheral nerve myelin (P0-glycoprotein) are: (1) to determine the three-dimensional structure of P0-glycoprotein for human and Xenopus. The proteins analyzed will include recombinant molecules having the native amino acid sequence, as well as those having specific sequence alterations known to occur in human peripheral neuropathies. These studies will inform about the atomic structure of P0 and about the crystal contacts or adhesion interfaces that may be responsible for the role of this protein in myelin formation and stability. (2) To characterize the protein-protein interactions between nearest-neighbor P0 molecules in a membrane mimetic environment using small-angle X-ray scattering. The membrane protein will be solubilized in aqueous solutions of detergents at very low concentration, and solution scattering will be undertaken using a synchrotron X-ray source. These studies will provide information about the interprotein molecular contacts that P0 molecules make in a milieu that more closely resembles its native environment (the lipid bilayer of the myelin membrane) than does a crystal. (3) To evaluate the membrane-membrane interactions in myelin of Xenopus peripheral nerves. Determining the pH- and ionic strength-dependence of membrane structure and packing in dissected peripheral nerves that have been incubated at different will provide strong constraints for testing hypotheses about the adhesion mechanisms of P0 at both the cytoplasmic and extracellular membrane appositions. This hierarchy of experimental objectives will allow the investigator to uniquely correlate structural data from the atomic to the molecular, to the membrane level, and thus contribute to an understanding of the structural biology of a membrane protein that figures significantly in both health and disease.