title: Complete localization of disulfide bonds in GM2 activator protein.
abstract: Lysosomal degradation of ganglioside GM2 by hexosaminidase A requires the presence of a small, non-enzymatic cofactor, the GM2-activator protein (GM2AP). Lack of functional protein leads to the AB variant of GM2-gangliosidosis, a fatal lysosomal storage disease. Although its possible mode of action and functional domains have been discussed frequently in the past, no structural information about GM2AP is available so far. Here, we determine the complete disulfide bond pattern of the protein. Two of the four disulfide bonds present in the protein were open to classical determination by enzymatic cleavage and mass spectrometry. The direct localization of the remaining two bonds was impeded by the close vicinity of cysteines 136 and 138. We determined the arrangement of these disulfide bonds by MALDI-PSD analysis of disulfide linked peptides and by partial reduction, cyanylation and fragmentation in basic solution, as described recently (Wu F, Watson JT, 1997, Protein Sci 6:391-398).
authors.affiliation: Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn, Germany.
authors.forename: C G
authors.initials: CG
authors.lastname: Schütte
authors.forename: T
authors.initials: T
authors.lastname: Lemm
authors.forename: G J
authors.initials: GJ
authors.lastname: Glombitza
authors.forename: K
authors.initials: K
authors.lastname: Sandhoff
mesh_terms: D000595:Amino Acid Sequence; D004220:Disulfides / Q000737:chemistry*; D010450:Endopeptidases / Q000378:metabolism; D049289:G(M2) Activator Protein; D005678:G(M2) Ganglioside / Q000378:metabolism; D005733:Gangliosidoses / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D004220:Disulfides; D049289:G(M2) Activator Protein; D010446:Peptide Fragments; D011506:Proteins; D011994:Recombinant Proteins; D005678:G(M2) Ganglioside; D010450:Endopeptidases