Crystal structure of saposin B reveals a dimeric shell for lipid binding
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Date
2003Author
Ahn, Victoria E.
Faull, Kym F.
Whitelegge, Julian P.
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Show full item recordAbstract
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 -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.