Structural Basis of Mucopolysaccharidosis Type II and Construction of a Database of Mutant Iduronate 2-Sulfatases

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is an X-linked genetic disorder caused by a deficiency of iduronate 2-sulfatase (IDS), and missense mutations comprising about 30% of the mutations responsible for MPS II result in heterogeneous phenotypes ranging from the severe to the attenuated form. To elucidate the basis of MPS II from the structural viewpoint, we built structural models of the wild type and mutant IDS proteins resulting from 131 missense mutations (phenotypes: 67 severe and 64 attenuated), and analyzed the influence of each amino acid substitution on the IDS structure by calculating the accessible surface area, the number of atoms affected and the root-mean-square distance. The results revealed that the amino acid substitutions causing MPS II were widely spread over the enzyme molecule and that the structural changes of the enzyme protein were generally larger in the severe group than in the attenuated one. Coloring of the atoms influenced by different amino acid substitutions at the same residue showed that the structural changes influenced the disease progression. Based on these data, we constructed a database of IDS mutations as to the structures of mutant IDS proteins.