Molecular investigations of a novel iduronate-2-sulfatase mutant in a Chinese patient.
BACKGROUND
Molecular investigations of iduronate-2-sulfatase (IDS) mutants for the X-linked lysosomal storage disease mucopolysaccharidosis type II (MPS II, Hunter disease), commonly depends on transient expression studies to verify a single nucleotide change to be pathogenic. In 2 severely affected patients, IDS missense mutations, c.1016T>C (novel) and c.1016T>G (known) were identified predicting the substitution of an ambivalent cyclic proline and a hydrophilic arginine respectively for the hydrophobic leucine at residue 339. We hypothesized that residue Leu339 may be functionally critical.


METHODS
We performed a study for the 2 mutations by in-situ mutagenesis, in vitro expression, and functional analysis.


RESULTS
Transient expression revealed that both the missense variants had stable mRNA but their residual enzyme activities remained <2.5% of normal level. The effect of the missense mutations on protein expression was detected by Western blot analysis. Both the missense mutations synthesized the precursor form but had reduced mature form of IDS.


CONCLUSIONS
The novel mutation p.L339P is a disease-causing mutation affecting maturation of the protein.
Lau
Kin-Chong
KC
Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China.
Lam
Ching-Wan
CW
D000293:Adolescent; D000328:Adult; D019943:Amino Acid Substitution; D002460:Cell Line; D002675:Child, Preschool; D002681:China; D005091:Exons; D006801:Humans; D007066:Iduronate Sulfatase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016532:Mucopolysaccharidosis II / Q000209:etiology / Q000235:genetics*; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D017354:Point Mutation
D007066:Iduronate Sulfatase