Screening Glycolipids Against Proteins in Vitro Using Picodiscs and Catch-and-Release Electrospray Ionization-Mass Spectrometry

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• 作者：Jun Li ; Xuxin Fan ; Elena N. Kitova ; Chunxia Zou ; Christopher W. Cairo ; Luiz Eugenio ; Kenneth K. S. Ng ; Zi Jian Xiong ; Gilbert G. Privé ; John S. Klassen
• 刊名：Analytical Chemistry
• 出版年：2016
• 出版时间：May 3, 2016
• 年：2016
• 卷：88
• 期：9
• 页码：4742-4750
• 全文大小：460K
• 年卷期：0
• ISSN：1520-6882

文摘

This work describes the application of the catch-and-release electrospray ionization-mass spectrometry (CaR-ESI-MS) assay, implemented using picodiscs (complexes comprised of saposin A and lipids, PDs), to screen mixtures of glycolipids (GLs) against water-soluble proteins to detect specific interactions. To demonstrate the reliability of the method, seven gangliosides (GM1, GM2, GM3, GD1a, GD1b, GD2, and GT1b) were incorporated, either individually or as a mixture, into PDs and screened against two lectins: the B subunit homopentamer of cholera toxin (CTB₅) and a subfragment of toxin A from Clostridium difficile (TcdA-A2). The CaR-ESI-MS results revealed that CTB₅ binds to six of the gangliosides (GM1, GM2, GM3, GD1a, GD1b, and GT1b), while TcdA-A2 binds to five of them (GM1, GM2, GM3, GD1a, and GT1b). These findings are consistent with the measured binding specificities of these proteins for ganglioside oligosaccharides. Screening mixtures of lipids extracted from porcine brain and a human epithelial cell line against CTB₅ revealed binding to multiple GM1 isoforms as well as to fucosyl-GM1, which is a known ligand. Finally, a comparison of the present results with data obtained with the CaR-ESI-MS assay implemented using nanodiscs (NDs) revealed that the PDs exhibited similar or superior performance to NDs for protein–GL binding measurements.