Direct AFM observation of saposin C-induced membrane domains in lipid bilayers: From simple to complex lipid mixtures

Hong Xing You, Xiaoyang Qi, Lei Yu

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Saposin C (Sap C) is a small glycoprotein required by glucosylceramidase (GCase) for hydrolysis of glucosylceramide to ceramide and glucose in lysosomes. The molecular mechanism underlying Sap C stimulation of the enzyme activation is not fully understood. Here, atomic force microscopy (AFM) has been used to study Sap C-membrane interactions under physiological conditions. First, to establish how Sap C-membrane interactions affect membrane structure, lipid bilayers containing zwitterionic and anionic phospholipids were used. It was observed that Sap C induced two types of membrane restructuring effects, i.e., the formation of patch-like domains and membrane destabilization. Bilayers underwent extensive structural reorganization. To validate the biological importance of the membrane restructuring effects, interaction of Sap C with lipid bilayers composed of cholesterol, sphingomyelin, and zwitterionic and anionic phospholipids were studied. Although similar membrane restructuring effects were observed, Sap C-membrane interactions, in this case, were remarkably modulated and their effects were restricted to a limited area. As a result, nanometer-sized domains were formed. The establishment of a model membrane system will allow us to further study the dynamics, structure and mechanism of the Sap C-associated membrane domains and to examine the important role that these domains may play in enzyme activation.

Original languageEnglish (US)
Pages (from-to)15-22
Number of pages8
JournalChemistry and Physics of Lipids
Issue number1
StatePublished - Oct 2004
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Organic Chemistry
  • Cell Biology


  • Atomic force microscopy
  • Lipid rafts
  • Membrane microdomains
  • Protein-lipid interaction
  • Saposins
  • Supported planar lipid bilayers


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