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Molecular imaging of membrane interfaces reveals mode of beta-glucosidase activation by saposin C.

ABSTRACT: Acid beta-glucosidase (GCase) is a soluble lysosomal enzyme responsible for the hydrolysis of glucose from glucosylceramide and requires activation by the small nonenzymatic protein saposin C (sapC) to gain access to the membrane-embedded glycosphingolipid substrate. We have used in situ atomic force microscopy (AFM) with simultaneous confocal and epifluorescence microscopies to investigate the interactions of GCase and sapC with lipid bilayers. GCase binds to sites on membranes transformed by sapC, and enzyme activity occurs at loci containing both GCase and sapC. Using FRET, we establish the presence of GCase/sapC and GCase/product contacts in the bilayer. These data support a mechanism in which sapC locally alters regions of bilayer for subsequent attack by the enzyme in stably bound protein complexes.

SUBMITTER: Alattia JR

PROVIDER: S-EPMC2077267 | biostudies-literature | 2007 Oct

REPOSITORIES: biostudies-literature

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Molecular imaging of membrane interfaces reveals mode of beta-glucosidase activation by saposin C.

Alattia Jean-René JR Shaw James E JE Yip Christopher M CM Privé Gilbert G GG

Proceedings of the National Academy of Sciences of the United States of America 20071022 44

Acid beta-glucosidase (GCase) is a soluble lysosomal enzyme responsible for the hydrolysis of glucose from glucosylceramide and requires activation by the small nonenzymatic protein saposin C (sapC) to gain access to the membrane-embedded glycosphingolipid substrate. We have used in situ atomic force microscopy (AFM) with simultaneous confocal and epifluorescence microscopies to investigate the interactions of GCase and sapC with lipid bilayers. GCase binds to sites on membranes transformed by s ...[more]

PMID: 17954913

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