title: Characterization of the N370S mutant of glucocerebrosidase by hydrogen/deuterium exchange mass spectrometry.
abstract: An asparagine-to-serine substitution at residue 370 (N370S) in glucocerebrosidase (GCase) is the most prevalent mutation leading to Gaucher's disease, the most common lysosomal storage disorder. Two types of hydrogen/deuterium exchange experiment coupled with proteolysis and liquid chromatography-mass spectrometry (HDX-MS) were used to investigate the dynamic properties and unfolding stability of wt, R495H, and N370S GCases in the presence and absence of ligands. R495H GCase is used for enzyme replacement therapy and is considered to be a wt surrogate, whereas N370S is the most prevalent mutation leading to Gaucher's disease. Time-course HDX experiments of the GCases were performed under near-physiological conditions to detect the protein's local unfolding motions at a submolecular level. In guanidine-titration experiments, HDX reactions were performed with various concentrations of a chemical denaturant to provide the global stability of the proteins. The two types of experiment showed that all three purified GCases, wt, R495H, and N370S, have virtually identical local unfolding motions and global stabilities in solution. Combined with previous X-ray crystallographic studies, which showed indistinguishable backbone conformations for N370S and R495H GCase mutants and very similar melting temperatures for the wt, R495H, and N370S mutants, all three GCases are likely to have virtually identical structural and dynamic properties in solution. The guanidine-titration experiments revealed that the pharmacological chaperone, isofagomine (IFG), interacts more weakly with the N370S mutant than with the R495H GCase; this is consistent with the higher IC(50)  value of IFG against N370S than against R495H. The time-course experiments showed that IFG restricts the local unfolding motions of N370S in the same way as those of R495H when the ligand saturates the proteins.
authors.affiliation: ExSAR Corporation, 11 Deer Park Drive, Suite 103, Monmouth Junction, NJ 08852, USA.
authors.forename: Liangjie
authors.initials: L
authors.lastname: Tang
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Coales
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Morrow
authors.forename: Tim
authors.initials: T
authors.lastname: Edmunds
authors.forename: Yoshitomo
authors.initials: Y
authors.lastname: Hamuro
mesh_terms: D019943:Amino Acid Substitution; D003903:Deuterium / Q000032:analysis; D005776:Gaucher Disease / Q000201:enzymology* / Q000235:genetics; D005962:Glucosylceramidase / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D050112:Imino Pyranoses / Q000494:pharmacology; D008024:Ligands; D013058:Mass Spectrometry; D017354:Point Mutation; D055550:Protein Stability / Q000187:drug effects; D058767:Protein Unfolding / Q000187:drug effects
chemical_list: D050112:Imino Pyranoses; D008024:Ligands; C098432:isofagomine; D006859:Hydrogen; D003903:Deuterium; D005962:Glucosylceramidase