Enhanced resolution of glycosylphosphatidylinositol‐anchored and transmembrane proteins from the lipid‐rich myelin membrane by two‐dimensional gel electrophoresis

Two-dimensional gel electrophoresis (2-DE) has become a powerful and widely used technique for proteomic analyses. However, the limited ability of 2-DE to resolve transmembrane and glycosylphosphatidylinositol (GPI)-anchored proteins has slowed the identification of proteins from membrane-rich biological samples. Myelin is an unusually lipid-rich membrane with relatively few major proteins but many quantitatively minor proteins, most of which have an unknown identity and/or function. The goal of this study was to identify the optimal conditions of 2-DE for the separation of myelin proteins. We have identified two detergents, the nonionic n-dodecyl beta-D-maltoside and the zwitterionic amidosulfobetaine ASB-14, that are more effective in solubilizing myelin proteins than the commonly used zwitterionic detergent 3-[(3-cholamidopropyl)- dimethylammonio]-1-propanesulfonate (CHAPS). These detergents significantly enhance the solubility of both transmembrane (e.g., the highly hydrophobic and multiply acylated myelin proteolipid protein) and GPI-anchored (e.g., contactin and neuronal cell adhesion molecule) myelin proteins and enable their resolution by 2-DE. We conclude that these detergents are effective tools for the 2-DE analysis of myelin, and that they may be more generally useful for the analysis of membrane-rich biological samples.