Proteomic analysis of detergent‐resistant membrane rafts

A combined, detergent‐ and organic solvent‐based proteomic method for the analysis of detergent‐resistant membrane rafts (DRMR) is described. These specialized domains of the plasma membrane contain a distinctive and dynamic protein and/or lipid complement, which can be isolated from most mammalian cells. Lipid rafts are predominantly involved in signal transduction and adapted to mediate and produce different cellular responses. To facilitate a better understanding of their biology and role, DRMR were isolated from Vero cells as a Triton X‐100 insoluble fraction. After detergent removal, sonication in 60% buffered methanol was used to extract, solubilize and tryptically digest the resulting protein complement. The peptide digestate was analyzed by microcapillary reversed‐phase liquid chromatography‐tandem mass spectrometry. Gas‐phase fractionation in the mass‐to‐charge range was employed to broaden the selection of precursor ions and increase the number of identifications in an effort to detect less abundant proteins. A total of 380 proteins were identified including all known lipid raft markers. A total of 91 (24%) proteins were classified as integral α‐helical membrane proteins, of which 51 (56%) were predicted to have multiple transmembrane domains.