Synthetic Glycoforms Reveal Carbohydrate‐Dependent Bioactivity of Human Saposin D

Abstract

The main glycoforms of the hydrophobic lysosomal glycoprotein saposin D( SapD) were synthesized by native chemical ligation. An approach for the challenging solid-phase synthesis of the fragments was developed. Three SapD glycoforms were obtained following ag eneral and robust refolding and purification protocol. Acrystal structure of one glycoform confirmed its native structure and disulfide pattern. Functional assays revealed that the lipid-binding properties of three SapD glycoforms are highly affected by the single sugar moiety of SapD showing ad ependency of the size and the type of Nglycan.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under http://dx.

Emerging concepts of ganglioside metabolism

“…It binds sulfatides in soluble stoichiometric complexes, which are recognized by arylsulfatase A as substrates . On the other hand, saposin C and D are lipid‐binding proteins, which can fuse lipid vesicles at low pH values, by that eventually bringing together newly formed ILVs with already processed, hydrolase loaded and BMP containing ILVs. The four saposins A, B, C, and D are generated in the lysosomal compartment by proteolytic cleavage of their precursor protein, prosaposin .…”

Building Peptide Bonds in Haifa: The Seventh Chemical Protein Synthesis (CPS) Meeting

“…The lysosomal N ‐glycoprotein saposin D (SapD) was synthesized in two segments that were ligated by NCL followed by successful refolding. Functional assays revealed that the lipid‐binding properties of SapD glycoforms are dependent on both the size and the nature of the glycan moiety . The biosynthesis of glycoproteins starts in the endoplasmic reticulum.…”

“…Functional assays revealed that the lipid-binding properties of SapD glycoforms are dependent on both the size and the natureo ft he glycan moiety. [24] The biosynthesis of glycoproteinss tarts in the endoplasmicr eticulum. To prevent the accumulation of deleterious misfoldedg lycoproteins, non-native glycoproteins are captured and converted into their native structures by chaperones.…”

Just a spoonful of sugar: Short glycans affect protein properties and functions

“…Because of the heterogeneous nature of this posttranslational modification, the investigation of the precise role of different glycans attached to a glycoprotein of therapeutic interest remains a very difficult task. In the last decades, great advances in protein engineering and, even more, in the chemical synthesis and semisynthesis of glycoproteins are giving access to homogeneous glycoproteins as tools for biological studies, thus enabling important progress in glycobiology. At the same time, the increasing rate of approval of glycoprotein therapeutics has fostered the research in the field, giving further impulse to the discovery of new preparation methods and to the studies on the effects of glycosylation on protein properties and functions, thus generating a virtuous circle.…”