Crystal Structure of saposin B reveals a dimeric shell for lipid bindingAhn, V.E., Faull, K.F., Whitelegge, J.P., Fluharty, A.L., Prive, G.G.
(2003) Proc Natl Acad Sci U S A 100: 38-43
- PubMed: 12518053
- DOI: https://doi.org/10.1073/pnas.0136947100
- Primary Citation of Related Structures:
- PubMed Abstract:
Saposin B is a small, nonenzymatic glycosphingolipid activator protein required for the breakdown of cerebroside sulfates (sulfatides) within the lysosome. The protein can extract target lipids from membranes, forming soluble protein-lipid complexes that are recognized by arylsulfatase A. The crystal structure of human saposin B reveals an unusual shell-like dimer consisting of a monolayer of alpha-helices enclosing a large hydrophobic cavity. Although the secondary structure of saposin B is similar to that of the known monomeric members of the saposin-like superfamily, the helices are repacked into a different tertiary arrangement to form the homodimer. A comparison of the two forms of the saposin B dimer suggests that extraction of target lipids from membranes involves a conformational change that facilitates access to the inner cavity.
Department of Medical Biophysics, University of Toronto, ON, Canada M5G 2M9.