Garman Scott C, Garboczi David N
Structural Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Twinbrook II, 12441 Parklawn Drive, Rockville, MD 20852, USA.
J Mol Biol. 2004 Mar 19;337(2):319-35. doi: 10.1016/j.jmb.2004.01.035.
Fabry disease is an X-linked lysosomal storage disease afflicting 1 in 40,000 males with chronic pain, vascular degeneration, cardiac impairment, and other symptoms. Deficiency in the lysosomal enzyme alpha-galactosidase (alpha-GAL) causes an accumulation of its substrate, which ultimately leads to Fabry disease symptoms. Here, we present the structure of the human alpha-GAL glycoprotein determined by X-ray crystallography. The structure is a homodimer with each monomer containing a (beta/alpha)8 domain with the active site and an antiparallel beta domain. N-linked carbohydrate appears at six sites in the glycoprotein dimer, revealing the basis for lysosomal transport via the mannose-6-phosphate receptor. To understand how the enzyme cleaves galactose from glycoproteins and glycolipids, we also determined the structure of the complex of alpha-GAL with its catalytic product. The catalytic mechanism of the enzyme is revealed by the location of two aspartic acid residues (D170 and D231), which act as a nucleophile and an acid/base, respectively. As a point mutation in alpha-GAL can lead to Fabry disease, we have catalogued and plotted the locations of 245 missense and nonsense mutations in the three-dimensional structure. The structure of human alpha-GAL brings Fabry disease into the realm of molecular diseases, where insights into the structural basis of the disease phenotypes might help guide the clinical treatment of patients.
法布里病是一种X连锁溶酶体贮积病，每40000名男性中就有1人患病，会出现慢性疼痛、血管退化、心脏损伤及其他症状。溶酶体酶α-半乳糖苷酶（α-GAL）缺乏会导致其底物蓄积，最终引发法布里病症状。在此，我们展示了通过X射线晶体学测定的人α-GAL糖蛋白的结构。该结构为同型二聚体，每个单体包含一个带有活性位点的（β/α）8结构域和一个反平行β结构域。N-连接碳水化合物出现在糖蛋白二聚体的六个位点，揭示了通过甘露糖-6-磷酸受体进行溶酶体转运的基础。为了解该酶如何从糖蛋白和糖脂中切割半乳糖，我们还测定了α-GAL与其催化产物的复合物结构。两个天冬氨酸残基（D170和D231）的位置揭示了该酶的催化机制，它们分别作为亲核试剂和酸碱。由于α-GAL中的点突变可导致法布里病，我们已在三维结构中标注并绘制了245个错义突变和无义突变的位置。人α-GAL的结构将法布里病带入分子疾病领域，对疾病表型结构基础的深入了解可能有助于指导患者的临床治疗。
