HIGH RESOLUTION STRUCTURAL STUDIES OF LIGAND BINDING DOMAIN OF LDL RECEPTOR

低密度脂蛋白受体（LDLR）是主要的 血浆胆固醇进入细胞的摄取机制， 作为细胞表面受体家族的原型。 这些 受体都利用串联重复的LDL-A模块来结合它们的 配体。 每个LDL-A模块长约40个残基，具有6个保守的 半胱氨酸残基，并含有一个保守的酸性区域附近的 作为钙结合位点的C末端。 的结构 这些模块提供的配体结合界面，以及 它们在配体结合中的特异性和亲和力的基础， 知道的 我们已经纯化了对应于LDL-A的重组分子， 模块五（LR 5）、六（LR 6 *）以及模块五-六对 （LR5-6*）。 需要钙来建立天然的 二硫键，并保持LR 5，LR 6 *， 和LR 5 -6* 模块对。 质子与多维的比较 单个模块的异向NMR谱与模块的异向NMR谱 对表明，大多数显着的光谱变化在于 在模块之间的接头区域内， 在5-6中的模块5和6的核心之间发生交互 汇率 这些发现有力地支持了一个模型，其中每个模块都是 在结构上彼此独立。 作业 主链和大多数侧链共振是完整的 用于LR 5、LR 6 * 和LR 5 -6* 模块对。 目前的努力 专注于完成侧链的分配和计算 LR 6 ~* 和LR 5 -6 ~* 的溶液结构。 我

The low-density lipoprotein receptor (LDLR) is the primary mechanism for the uptake of plasma cholesterol into cells and serves as a prototype for a growing family of cell surface receptors. These receptors all utilize tandemly-repeated LDL-A modules to bind their ligands. Each LDL-A module is about 40 residues long, has 6 conserved cysteine residues and contains a conserved acidic region near the C-terminus that serves as a calcium binding site. The structure of the interface presented for ligand binding by these modules, and the basis for their specificity and affinity in ligand binding, is not yet known. We have purified recombinant molecules corresponding to LDL-A modules five (LR5), six (LR6*), as well as the module five-six pair (LR5-6*) of the LDL receptor. Calcium is required to establish native disulfide bonds and to maintain the structural integrity of LR5, LR6*, and the LR5-6* module pair. Comparison of proton and multidimensional heteronuclear NMR spectra of individual modules to those of the module pair indicates that most of the significant spectroscopic changes lie within the linker region between modules and that little structural interaction occurs between the cores of modules 5 and 6 in the 5-6 pair. These findings strongly support a model in which each module is essentially structurally independent of the other. Assignments for the backbone and for most of the side chain resonances are complete for LR5, LR6*, and for the LR5-6* module pair. Current efforts are focused on completion of the side chain assignments and calculation of the solution structures of LR6* and LR5-6*. I