Dissociation of glucocerebrosidase dimer in solution by its co-factor, saposin C.

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TitleDissociation of glucocerebrosidase dimer in solution by its co-factor, saposin C.
Publication TypeJournal Article
Year of Publication2015
AuthorsGruschus, JM, Jiang, Z, Yap, TLeong, Hill, SA, Grishaev, A, Piszczek, G, Sidransky, E, Lee, JC
JournalBiochem Biophys Res Commun
Volume457
Issue4
Pagination561-6
Date Published2015 Feb 20
ISSN1090-2104
Keywordsalpha-Synuclein, Catalytic Domain, Gaucher Disease, Glucosylceramidase, Humans, Models, Molecular, Nuclear Magnetic Resonance, Biomolecular, Parkinson Disease, Protein Multimerization, Protein Stability, Saposins
Abstract

Mutations in the gene for the lysosomal enzyme glucocerebrosidase (GCase) cause Gaucher disease and are the most common risk factor for Parkinson disease (PD). Analytical ultracentrifugation of 8 μM GCase shows equilibrium between monomer and dimer forms. However, in the presence of its co-factor saposin C (Sap C), only monomer GCase is seen. Isothermal calorimetry confirms that Sap C associates with GCase in solution in a 1:1 complex (Kd = 2.1 ± 1.1 μM). Saturation cross-transfer NMR determined that the region of Sap C contacting GCase includes residues 63-66 and 74-76, which is distinct from the region known to enhance GCase activity. Because α-synuclein (α-syn), a protein closely associated with PD etiology, competes with Sap C for GCase binding, its interaction with GCase was also measured by ultracentrifugation and saturation cross-transfer. Unlike Sap C, binding of α-syn to GCase does not affect multimerization. However, adding α-syn reduces saturation cross-transfer from Sap C to GCase, confirming displacement. To explore where Sap C might disrupt multimeric GCase, GCase x-ray structures were analyzed using the program PISA, which predicted stable dimer and tetramer forms. For the most frequently predicted multimer interface, the GCase active sites are partially buried, suggesting that Sap C might disrupt the multimer by binding near the active site.

DOI10.1016/j.bbrc.2015.01.024
Alternate JournalBiochem. Biophys. Res. Commun.
PubMed ID25600808
PubMed Central IDPMC4361889
Grant ListZIA HL006144-03 / / Intramural NIH HHS / United States