Binding of GM1-ganglioside to a synthetic peptide derived from the lysosomal sphingolipid-activator-protein saposin B.
Saposin B is a lysosomal sphingolipid-activator-protein which activates GM1-ganglioside hydrolysis by lysosomal beta-galactosidase. To identify the structural elements of saposin B implicated in sphingolipid binding, we studied a synthetic peptide corresponding to a predicted alpha-helix, sapB-18, spanning residues 52 to 69 of saposin B. The circular dichroism spectrum of sapB-18 at pH 4.4 was consistent with a 44% alpha-helix content. As shown by intrinsic Tyr fluorescence studies of sapB-18, this peptide binds the GM1-ganglioside with a Kd of about 7 microM. Thus, we suggest that a putative amphipathic alpha-helix between residues 52 and 69 of saposin B plays a major role in the recognition and binding of GM1-ganglioside by saposin B.
Champagne
M J
MJ
Service de Génétique Médicale, Hôpital Sainte-Justine, Montréal, Québec, Canada.
Lamontagne
S
S
Potier
M
M
D000595:Amino Acid Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D005677:G(M1) Ganglioside / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D049231:Saposins; D013050:Spectrometry, Fluorescence; D049128:Sphingolipid Activator Proteins
D006023:Glycoproteins; D010446:Peptide Fragments; D049231:Saposins; D049128:Sphingolipid Activator Proteins; D005677:G(M1) Ganglioside