Structural Characterization of the E2 Domain of APL-1, a Caenorhabditis elegans Homolog of Human Amyloid Precursor Protein, and Its Heparin Binding Site
Structural Characterization of the E2 Domain of APL-1, a Caenorhabditis elegans Homolog of Human Amyloid Precursor Protein, and Its Heparin Binding Site
复制标题
DOI：
10.1074/jbc.m109.018432
复制
发表时间：
2010-01-15
影响因子：
4.8
通讯作者：
Ha, Ya
中科院分区：
文献类型：
--
作者：
Hoopes, James T.;Liu, Xuying;Ha, Ya
在阿尔茨海默病患者脑组织中发现的淀粉样β-肽沉积来自于一个大的肝素结合蛋白前体APP。APP及其同系物的生物学功能还不是很清楚。在这里，我们报告了APL-1的E2结构域的X射线结构，并将其与人类APP结构进行了比较。APL-1是秀丽线虫的APP同源基因。我们还描述了APL-1E2与蔗糖八硫酸盐的络合物的结构，这是一种高度负电的二糖，揭示了E2的两半之间意想不到的结合口袋。基于晶体结构，我们能够利用定点突变，在E2上定位肝素可能与之结合的表面凹槽。我们的生化数据还表明，E_2对肝素的亲和力受pH的影响：在pH为5时，结合似乎比在中性pH时强得多。这一特性可能是由映射的肝素结合位点附近的组氨酸残基引起的，并可能对APL-1的拟议黏附功能起重要作用。
The amyloid beta-peptide deposit found in the brain tissue of patients with Alzheimer disease is derived from a large heparin-binding protein precursor APP. The biological function of APP and its homologs is not precisely known. Here we report the x-ray structure of the E2 domain of APL-1, an APP homolog in Caenorhabditis elegans, and compare it to the human APP structure. We also describe the structure of APL-1 E2 in complex with sucrose octasulfate, a highly negatively charged disaccharide, which reveals an unexpected binding pocket between the two halves of E2. Based on the crystal structure, we are able to map, using site-directed mutagenesis, a surface groove on E2 to which heparin may bind. Our biochemical data also indicate that the affinity of E2 for heparin is influenced by pH: at pH 5, the binding appears to be much stronger than that at neutral pH. This property is likely caused by histidine residues in the vicinity of the mapped heparin binding site and could be important for the proposed adhesive function of APL-1.