Abstract
Proteomics analysis of plasma membranes from cells exposed to different extracellular environments is potentially a powerful approach for the identification of membraneโassociated proteins responding to these environments. Preparation of high concentration plasma membrane fractions with low contamination from cellular organelles is essential for such studies. Here, we describe an affinity enrichment method, which combines cell surface biotinylation with affinity enrichment by immobilized streptavidin beads, for the isolation of plasma membranes. This method results in a 400โfold enrichment of plasma membrane relative to endoplasmic reticulum, a major contaminant in standard plasma membrane preparations, and dramatically reduces contamination from other cellular organelles. The biotinylation reaction did not interfere with ligandโdependent activation of receptor tyrosine kinases or Gโprotein coupled receptors, suggesting cellโsurface signal transduction machinery remains functional. Membrane fractions prepared by this method should provide excellent starting materials for membrane proteomics analysis such as studies of dynamic trafficking and regulation of signaling molecules or identification of diseaseโspecific membrane markers.