The molecular defect leading to Fabry disease: structure of human alpha-galactosidase.
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.
Garman
Scott C
SC
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. sgarman@niaid.nih.gov
Garboczi
David N
DN
D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000737:chemistry; D020134:Catalytic Domain; D018389:Codon, Nonsense; D018360:Crystallography, X-Ray; D019281:Dimerization; D019143:Evolution, Molecular; D000795:Fabry Disease / Q000201:enzymology* / Q000235:genetics*; D006801:Humans; D008247:Lysosomes / Q000201:enzymology; D008297:Male; D008958:Models, Molecular; D020125:Mutation, Missense; D010802:Phylogeny; D011487:Protein Conformation; D055672:Static Electricity; D013379:Substrate Specificity; D000519:alpha-Galactosidase / Q000737:chemistry / Q000235:genetics*
D002241:Carbohydrates; D018389:Codon, Nonsense; D000519:alpha-Galactosidase