Off-campus UMass Amherst users: To download campus access dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.

Non-UMass Amherst users: Please talk to your librarian about requesting this dissertation through interlibrary loan.

Dissertations that have an embargo placed on them will not be available to anyone until the embargo expires.

Author ORCID Identifier


Campus-Only Access for One (1) Year

Document Type


Degree Name

Doctor of Philosophy (PhD)

Degree Program

Molecular and Cellular Biology

Year Degree Awarded


Month Degree Awarded


First Advisor

Scott C. Garman

Subject Categories

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

cognate hydrolases.


Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.