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Author ORCID Identifier
Campus-Only Access for One (1) Year
Doctor of Philosophy (PhD)
Molecular and Cellular Biology
Year Degree Awarded
Month Degree Awarded
Scott C. Garman
Biochemistry, Biophysics, and Structural Biology
Saposins are helix bundle proteins which solubilize sphingolipids and present
them to lysosomal hydrolases for catabolism. Saposin B (SapB) is an activator of
globotriaosylceramide (Gb3) catabolism by α-galactosidase A (GLA). The
mechanism by which SapB activates GLA is unknown. SapB forms dimeric
water-soluble lipoprotein complexes in vitro and presents a restrictive
conformation in crystal structures. To uncover the molecular mechanism of SapB
presenting to GLA, we subjected the fluorescent substrate derivate Gb3NBD to a
series of assays involving SapB. Firstly, we showed that SapB stably binds
Gb3NBD and presents it to GLA for cleavage in vitro. Secondly, we crystallized
SapB in the presence of Gb3NBD. Thirdly, we showed that transient interactions
between SapB and GLA can be chemically cross-linked. Fourthly, we crystallized
SapB in the presence of detergent, which detergent also led to the capture of a
binary complex between SapB and GLA. These findings provide direction for
future biochemical and structural studies on the remaining saposins and their
Sawyer, Thomas K., "Human Saposin B Ligand Binding and Presentation to α-Galactosidase A" (2022). Doctoral Dissertations. 2569.
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